Anodes for improved detection of non-collected adjacent signals

ABSTRACT

A radiation detector assembly is provided that includes a semiconductor detector, a collimator, plural pixelated anodes, and at least one processor. The collimator has openings defining pixels. Each pixelated anode is configured to generate a primary signal responsive to reception of a photon and to generate at least one secondary signal responsive to reception of a photon by at least one surrounding anode. Each pixelated anode includes a first portion and a second portion located in different openings of the collimator. The first portion is configured as a collecting portion having a collecting area, and the second portion is configured as a non-collecting portion having a non-collecting area that has a different size from the collecting area. The at least one processor is configured to determine a location for the reception of a photon using a primary signal and at least one secondary signal.

RELATED APPLICATIONS

This application is a continuation-in-part of and claims priority toU.S. patent application Ser. No. 15/998,449, entitled “Anodes forImproved Detection of Non-Collected Adjacent Signals,” and filed Aug.15, 2018, the entire subject matter of which is hereby incorporated byreference in its entirety.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates generally to apparatus andmethods for diagnostic medical imaging, such as Nuclear Medicine (NM)imaging.

In NM imaging, for example, systems with multiple detectors or detectorheads may be used to image a subject, such as to scan a region ofinterest. For example, the detectors may be positioned adjacent thesubject to acquire NM data, which is used to generate athree-dimensional (3D) image of the subject.

Imaging detectors may be used to detect reception of photons from anobject (e.g., human patient or animal body that has been administered aradiotracer) by the imaging detector. Reception of photons may result incollected signals in primary pixels under which a given photon isabsorbed, and non-collected signals resulting from induced charges inone or more pixels adjacent to the primary pixel. The non-collectedsignals from adjacent pixels may be used, for example, to determineposition of a primary event in a primary pixel at a sub-pixel level.Non-collected signals, however, tend to be relatively weak and maysuffer from poor signal-to-noise ratio (SNR), reducing the effectivenessor accuracy of the use of the non-collected signals.

BRIEF DESCRIPTION OF THE INVENTION

In one embodiment, a radiation detector assembly is provided thatincludes a semiconductor detector, a collimator, plural pixelatedanodes, and at least one processor. The semiconductor has a surface. Thecollimator is disposed above the surface, and has openings definingpixels. The plural pixelated anodes are disposed on the surface. Eachpixelated anode is configured to generate a primary signal responsive toreception of a photon by the pixelated anode and to generate at leastone secondary signal responsive to an induced charge caused by receptionof a photon by at least one surrounding anode. Each pixelated anodeincludes a first portion and a second portion located in differentopenings of the collimator. The at least one processor is operablycoupled to the pixelated anodes, and configured to acquire a primarysignal from one of the pixelated anodes responsive to reception of aphoton by the one of the anodes; acquire at least one secondary signalfrom at least one neighboring pixelated anode of the one of thepixelated anodes responsive to an induced charge caused by the receptionof the photon by the one of the anodes; and determine a location for thereception of the photon using the primary signal and the at least onesecondary signal.

In another embodiment, a radiation detector assembly is provided thatincludes a semiconductor detector, a collimator, plural pixelatedanodes, and at least one processor. The semiconductor has a surface. Thecollimator is disposed above the surface, and has openings definingpixels. The plural pixelated anodes are disposed on the surface. Eachpixelated anode is configured to generate a primary signal responsive toreception of a photon by the pixelated anode and to generate at leastone secondary signal responsive to an induced charge caused by receptionof a photon by at least one surrounding anode. Each anode unit-structureincludes a first portion and a second portion that form portions ofdifferent pixelated anodes located in different pixels corresponding tothe different openings of the collimator. The at least one processor isoperably coupled to the pixelated anodes, and configured to acquire aprimary signal from one of the pixelated anodes responsive to receptionof a photon by the one of the anodes; acquire at least one secondarysignal from at least one neighboring pixelated anode of the one of thepixelated anodes responsive to an induced charge caused by the receptionof the photon by the one of the anodes; and determine a location for thereception of the photon using the primary signal and the at least onesecondary signal.

In another embodiment, a method is provided that includes providing asemiconductor substrate. The method also includes providing anodeunit-structures on the semiconductor substrate, with each of the anodeunit-structures including anode strips configured to receive electricalcharge responsive to absorption of a photon. Further, the methodincludes arranging the plural anode unit-structures into correspondinganode unit-cells, with each anode unit cell including at least two anodeunit-structures. Also, the method includes arranging the anodeunit-cells into pixelated anodes, wherein at least a first portion andsecond portion of each anode unit-structure form portions of differentpixels wherein each pixel is defined by an opening of a collimatorplaced above the unit-cells.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a representation of weighting potentials of a detectorhaving a pixel biased by a voltage potential.

FIG. 2 illustrates a graph of an induced integrated charge Q on a pixelof the detector of FIG. 1.

FIG. 3 schematically illustrates an assembly including a detectorincluding pixelated anodes.

FIG. 3a schematically illustrates a graph showing an induced charge Q ona pixelated anode by charge clouds as a function of time.

FIG. 3b schematically illustrates a graph showing an induced charge Q ona pixelated anode by charge clouds as a function of time.

FIG. 3c schematically illustrates a graph showing an induced charge Q ona pixelated anode by charge clouds as a function of time.

FIG. 3d schematically illustrates a graph showing an induced charge Q ona pixelated anode by charge clouds as a function of time

FIG. 4a provides a plan view of an anode unit-structure in accordancewith various embodiments.

FIG. 4b provides a side sectional view of the anode unit-structure ofFIG. 4 a.

FIG. 4c provides an end sectional view of the anode unit-structure ofFIG. 4 a.

FIG. 5a provides a schematic plan view of insulating layers of an anodeunit-structure in accordance with various embodiments.

FIG. 5b schematically illustrates grids (or fork-like structures in theillustrated example) of the anode unit-structure of FIG. 5 a.

FIG. 5c provides a schematic top view of the anode unit-structure ofFIG. 5 a.

FIG. 5d provides an exploded view of the grids of FIG. 5 b.

FIG. 6 provides a schematic plan view of an anode unit-cell thatincludes four anode unit-structures in accordance with variousembodiments.

FIG. 7 provides a schematic top view of a radiation imaging detector inaccordance with various embodiments.

FIG. 8a shows an enlarged view of aspects of the collimator of FIG. 8 b.

FIG. 8b schematically depicts a collimator having nine openings inaccordance with various embodiments.

FIG. 9a provides a schematic depiction of butting of unit-cells invarious embodiments.

FIG. 9b provides a schematic depiction of butting of unit-cells invarious embodiments.

FIG. 9c provides a schematic depiction of butting of unit-cells invarious embodiments.

FIG. 10a schematically illustrates a unit-cell 400 in accordance withvarious embodiments.

FIG. 10b schematically illustrates the relative position between theunit-cell of FIG. 10a and a part of an associated collimator inaccordance with various embodiments.

FIG. 10c schematically illustrates the area of butted anode unit-cells400 as being equal to the area under collimator 420.

FIG. 11 is a schematic illustration of an electronic channel inside anASIC used in various embodiments.

FIG. 12 provides a schematic side view of a radiation detector assemblyin accordance with various embodiments.

FIG. 13 provides a top view of a semiconductor detector of the radiationdetector assembly of FIG. 12.

FIG. 14 provides an enlarged plan view of aspects of the radiationdetector assembly of FIG. 12.

FIG. 15 provides a flowchart of a method in accordance with variousembodiments.

FIG. 16 provides a schematic view of an imaging system in accordancewith various embodiments.

FIG. 17 provides a schematic view of an imaging system in accordancewith various embodiments.

FIG. 18 provides a schematic view of a detector system having an offsetcollimator and pixelated anodes in accordance with various embodiments.

FIG. 19a provides a schematic plan view of insulating layers of an anodeunit-structure in accordance with various embodiments.

FIG. 19b schematically illustrates grids (or fork-like structures in theillustrated example) of the anode unit-structure of FIG. 19 a.

FIG. 19c provides a schematic top view of the anode unit-structure ofFIG. 19 a.

FIG. 19d provides an exploded view of the grids of FIG. 19 b.

FIG. 20a provides a schematic plan view of insulating layers of an anodeunit-structure in accordance with various embodiments.

FIG. 20b schematically illustrates grids (or fork-like structures in theillustrated example) of the anode unit-structure of FIG. 20 a.

FIG. 20c provides a schematic top view of the anode unit-structure ofFIG. 20 a.

FIG. 20d provides an exploded view of the grids of FIG. 20 b.

FIG. 21a is a schematic top view of an anode unit-cell including acentral collecting area in accordance with various embodiments.

FIG. 21b is a schematic top view of a collecting portion of a pixeldefined by the anode unit-cell of FIG. 21 a.

FIG. 21c is a schematic top view of a non-collecting portion of a pixeldefined by the anode unit-cell of FIG. 21 a.

FIG. 22 provides a sectional view of a system including a unit-cell anda circuit board in accordance with various embodiments.

FIG. 23 provides a flowchart of a method in accordance with variousembodiments.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description of certain embodiments will be betterunderstood when read in conjunction with the appended drawings. To theextent that the figures illustrate diagrams of the functional blocks ofvarious embodiments, the functional blocks are not necessarilyindicative of the division between hardware circuitry. For example, oneor more of the functional blocks (e.g., processors or memories) may beimplemented in a single piece of hardware (e.g., a general purposesignal processor or a block of random access memory, hard disk, or thelike) or multiple pieces of hardware. Similarly, the programs may bestand alone programs, may be incorporated as subroutines in an operatingsystem, may be functions in an installed software package, and the like.It should be understood that the various embodiments are not limited tothe arrangements and instrumentality shown in the drawings.

As used herein, the terms “system,” “unit,” or “module” may include ahardware and/or software system that operates to perform one or morefunctions. For example, a module, unit, or system may include a computerprocessor, controller, or other logic-based device that performsoperations based on instructions stored on a tangible and non-transitorycomputer readable storage medium, such as a computer memory.Alternatively, a module, unit, or system may include a hard-wired devicethat performs operations based on hard-wired logic of the device.Various modules or units shown in the attached figures may represent thehardware that operates based on software or hardwired instructions, thesoftware that directs hardware to perform the operations, or acombination thereof.

“Systems,” “units,” or “modules” may include or represent hardware andassociated instructions (e.g., software stored on a tangible andnon-transitory computer readable storage medium, such as a computer harddrive, ROM, RAM, or the like) that perform one or more operationsdescribed herein. The hardware may include electronic circuits thatinclude and/or are connected to one or more logic-based devices, such asmicroprocessors, processors, controllers, or the like. These devices maybe off-the-shelf devices that are appropriately programmed or instructedto perform operations described herein from the instructions describedabove. Additionally or alternatively, one or more of these devices maybe hard-wired with logic circuits to perform these operations.

As used herein, an element or step recited in the singular and precededwith the word “a” or “an” should be understood as not excluding pluralof said elements or steps, unless such exclusion is explicitly stated.Furthermore, references to “one embodiment” of are not intended to beinterpreted as excluding the existence of additional embodiments thatalso incorporate the recited features. Moreover, unless explicitlystated to the contrary, embodiments “comprising” or “having” an elementor a plurality of elements having a particular property may includeadditional elements not having that property.

Various techniques may be employed to improve the quality of X-Ray andGamma ray imaging using virtual sub-pixilation. Examples of such methodsinclude those discussed in U.S. Pat. No. 9,696,440, “Systems and methodsfor improving energy resolution by sub-pixel energy calibration,” issuedJul. 4, 2017; U.S. Pat. No. 9,632,186, “Systems and methods forsub-pixel location determination,” issued Apr. 25, 2017: and U.S. patentapplication Ser. No. 15/613,998, filed Jun. 5, 2017 and published asU.S. Published Application No. 2017/0269240 “Systems and methods forimproving imaging by sub-pixel calibration,” published on Sep. 21, 2017,all of which are hereby incorporated by reference in their entirety.

The virtual division of physical pixels into virtual sub-pixels may beperformed by identifying the coordinates of the event location withinthe physical pixels and assigning the events, according to theirposition coordinates in the physical pixels, to the sub-pixels intowhich the physical pixels are divided. The location of events inside thephysical pixels may be identified based on the weighted average of thenon-collected transient signals induced on the anodes of the pixels,which are adjacent to the primary pixel in which the event (theabsorbing of a photon by the primary pixel) occurs.

However, the non-collected induced transient signals, in the pixelsadjacent to the primary pixel, may be weak and suffer from poorSignal-To-Noise-Ratio (SNR). Poor SNR for the non-collected inducedtransient signals may result in error in deriving the position of theevents inside the physical primary pixels, which degrades the efficiencyof the use of virtual sub-pixelization to improve the image quality ofthe X-Ray and Gamma ray imaging systems.

Accordingly, various embodiments provide detectors and methods toimprove the SNR of the measured non-collected transient induced signalsin the pixels adjacent to the primary pixels. For example, variousembodiments provide anode geometry that enhances the amplitude of themeasured non-collected transient induced signals in the pixels adjacentto the primary pixels. Additionally or alternatively, variousembodiments provide pixelated anode geometry that includes collectingand non-collecting regions in the same anode. For example, variousembodiments provide the collecting and non-collecting regions in thepixilated anodes in a form of grid or strips. It may be noted thatvarious embodiments define the collecting and non-collecting regions inthe pixelated anodes by the relative position between an associatedcollimator and pixelated detector.

Generally, in conventional configurations, the non-collected signal inthe adjacent pixels is induced by a charge in the primary pixels, whichis relatively far away from the adjacent pixel where the electricalfield of the weighting potential is weak, resulting in weaknon-collected induced signals. Various embodiments disclosed hereinimprove imaging by enhancing the adjacent non-collected inducedtransient signals using a configuration in which the non-collectedinduced signal in the adjacent pixels are produced by the charge in theprimary pixel when the charge moves under the non-collecting anode ofthe adjacent pixels which is located in the region of the primary pixel.Accordingly, the adjacent non-collected induced transient signals areproduced where the electrical field of the weighting potential isstronger, resulting in stronger non-collected induced signals.

Before addressing specific aspects of example embodiments, the behaviorof detectors impacted photons is first discussed. FIG. 1 shows,according to Shockley-Ramo theorem, the weighting potential of a pixel12 (or pixelated anode), in a pixelated detector 10, that is biased by apotential of 1V while the surrounding anodes 14 and the cathode 16 aregrounded (V=0). The detector 10 may be fabricated, for example, from asemiconductor wafer 11, which may be made of CdTe, CdZnTe (CZT), Ge orSi. (It may be noted in practice that, for example, the pixel 12 andanodes 14 may be biased at the same voltage in practice; however thebiasing of FIG. 1 is provided for ease and clarity of description ofcertain aspects of detector behavior.)

According to this theorem, the induced current produced in pixel 12 (orpixelated anode 12), by the weighting potential, is given by theequation (1): Eq. (1) i=qE*V=qE*V*cos(a), where i is the inducedcurrent, q is the electron charge moving in detector 10 having athickness D in a Z direction, and E*V is the scalar product between thevector of the electrical field E of the weighting potential and thevector of the velocity V of the electron, and (a) is the angle betweenthe vectors E and V. (It may be noted that i is the induced current onan electrode having potential of 1V thus, units wise, the left side ofthe equation above may be multiplied by 1V to provide the proper units;however, this will not change the absolute value of the inducedcurrent.)

In operation, pixel 12 and anodes 14 (or pixelated anodes 12, 14) of thedetector 10 have high potential relative to the cathode 16. As notedabove, the bias of 1V for the pixel 12 and bias of 0V for anodes 14 andcathode 16, as depicted by FIG. 1, are shown as such for clarity indepicting the calculation of the weighting potential of the pixel 12. Asseen in FIG. 1, the weighting potential of pixel 12 includesequipotential lines 18 illustrated by broken lines and electrical fieldlines 20.

When the pixel 12 is a non-collecting pixel (e.g., when a pixel or anodeadjacent to the pixel 12 is collecting pixel), the charges at points 22,24 and 26 moving toward pixel 14 induce current or charge onnon-collecting pixel 12 according to equation (1) above. It may be notedthat in range I, the charge induced on the pixel 12 by the chargesmoving from points 22, 24 and 26 toward anode 14, is positive (Q>0)according to equation (1), since, in this range, the scalar product ofthe orientation of the lines of the electrical field E with theorientation of the velocity V of the moving charges multiplied by thepolarity of the charges q is positive. However, in range II, the inducedcharge, by the charges moving from points 22, 24 and 26 toward anode 14,on anode 12 is negative (Q<0) according to equation (1) since, in thisrange, the scalar product of the orientation of the lines of theelectrical field E with the orientation of the velocity V of the movingcharges multiply by the polarity of the charges q is negative. It may benoted that the charges starting at points 22 and 26 move toward theanode 14 along trajectory 28. Similarly, the charge starting at point 24moves toward the anode 24 along trajectory 30.

Accordingly, it may be seen from FIG. 1 that the electrical field of theweighted potential is stronger under an anode than away from an anode.Accordingly, if the anode 14 were biased by a potential that is higherthan that of the pixel 12, the charge created by an event under thepixel 12 at point 24 would be collect by the anode 14 while moving alongtrajectory 30 under the pixel 12. At the same time, such an event wouldinduce a non-collected charge on the pixel 12 which is much strongerthan the non-collected charge induced on the pixel 12 by an eventcreated under the anode 14 at point 22 that moves in a conventional wayalong trajectory 28 to be collected by the anode 14.

FIG. 2 illustrates a graph 100 of the induced integrated charge Q on thepixel 12 as a function of the coordinate Z, in detector 10, of thecharges moving toward the anode 14 of the detector 10. Included in thegraph 100 are curves 102, 104 and 106 of the non-collected inducedtransient signals produced on the pixel 12 by the charges moving frompoints 24, 22 and 26, respectively, toward the anode 14 alongtrajectories 28 and 30. It may be noted that the signal 102 is strongerthan the signals 104, 106, because the charge created by the event forsignal 102 moves under the non-collecting anode on which it induces thenon-collecting signal.

The induced integrated charge Q of the curve 102 increases in range Ialong trajectory 30 where positive charge is induced on the pixel 12 anddecreases in range II along trajectory 30 where negative integratedcharge is induced on the pixel 12. At point Z=D the induced charge Q₁₀₂on the pixel 12 is zero as shown by equation (2): Eq. (2)Q₁₀₂=Q(I)₁₀₂−Q(II)₁₀₂=0, where Q(I)₁₀₂ and Q(II)₁₀₂ are the inducedcharges on pixels 12 in regions I and II, respectively

Similarly, the induced integrated charge Q of curve 104 increases inrange I along trajectory 28 where positive charge is induced on anode12, and decreases in range II along trajectory 28 where negativeintegrated charge is induced on anode 12. At point Z=D the inducedcharge Q₁₀₄ on the pixel 12 is zero as shown by equation (2): Eq. (3)Q₁₀₄=Q(I)₁₀₄−Q(II)₁₀₄=0, where Q(I)₁₀₄ and Q(II)₁₀₄ are the inducedcharges on pixel 12 in regions I and II, respectively.

It may be noted that curve 104 represents an induced integrated chargeQ₁₀₄ that is smaller than the integrated charge Q₁₀₂ represented bycurve 102, because curve 104 is for trajectory 28 (see FIG. 1), which islocated more remotely from the pixel 12 than trajectory 30 for curve 102is. Accordingly, the electrical field of the weighting potential forcurve 104 is smaller than that for curve 102, resulting in smallerinduced integrated charge Q₁₀₄ for curve 104 than for curve 102.

The induced charge Q₁₀₆ of curve 106 goes up in range I along trajectory28 where positive charge is induced on the pixel 12 and goes down inrange II along trajectory 28 where negative charge is induced on thepixel 12. Since for curve 106 the charges start to move from point 26,the integration range along trajectory 28 within range I is shorter thanthat discussed above for curve 104. Accordingly, the positive integratedcharge in region I Q(I)₁₀₆ for curve 106 is smaller than the positiveintegrated charge in region I Q(I)₁₀₄ for curve 104. Both curve 106 andcurve 104 have the same integrated negative charge in range II(−Q(II)₁₀₄=−Q(II)₁₀₆). Accordingly, since the positive integrated chargeQ of curve 106 is smaller than this of curve 104 (Q(I)₁₀₆−<Q(I)₁₀₄), andsince they both have the same negative integrated charge(Q(II)₁₀₆−=Q(II)₁₀₄), the induced charge at Z=D for curve 106 isnegative as shown below by equation (4) and (6).

For example, equation (4) is as follows: Eq. (4) Q₁₀₆=Q(I)₁₀₆−Q(II)₁₀₆.Since (Q(II)₁₀₆−=Q(II)₁₀₄), then: Eq. (5)Q₁₀₆=Q(I)₁₀₆−Q(II)₁₀₆=Q(I)₁₀₆−Q(II)₁₀₄. Since (Q(I)₁₀₆−<Q(I)₁₀₄), and atZ=D Q₁₀₄=Q(I)₁₀₄−Q(II)₁₀₄=0, then: Eq. (6)Q₁₀₆=Q(I)₁₀₆−Q(II)₁₀₆=Q(I)₁₀₆−Q(II)₁₀₄<Q(I)₁₀₄−Q(II)₁₀₄=0. Accordingly,Q₁₀₆=Q(I)₁₀₆−Q(II)₁₀₆<0.

It may be noted that the negative value of the induced charge Q₁₀₆ onpixel 12 at Z=D is kept almost constant on Charge Sensitive Amplifies(CSA) such as CSA 202 shown in FIG. 3. The negative integrated chargeQ₁₀₆ on CSA 202 slowly decays toward a value of zero with a timeconstant τ that is equal to the product of the feedback capacitor C₂₀₄and the feedback resistor R₂₀₆ of CSA 202 (see FIG. 3).

From FIG. 2, it may be seen that the farther away is the trajectory ofthe moving charges collected by the anode 14 from the pixel 12, thesmaller is the amplitude of the non-collected induced signals on thepixel 12.

FIG. 3 schematically illustrates an assembly 200 including a detector210 including pixelated anodes 212, 214 and 216. The pixelated anodes212, 214, and 216 in various embodiments are coupled to CSA's such asCSA 202 including feedback capacitor 204 and resistor 206. Theillustrated detector 210 has a monolithic cathode 208. The pixelatedanodes (or pixels) 212, 214 and 216 are positively biased with respectto the cathode 208 and have voltages V, V, and V-ΔV relative to cathode208, respectively.

As seen in FIG. 3, charge cloud 218 is formed by absorbing a photon inthe detector 210 near the cathode 208. The charge cloud 218 moves alongtrajectory 232 and, close to anodes 212 and 214, is split into twocharge clouds 218 a and 218 b moving along trajectories 224 and 226toward pixels 212 and 214, respectively.

FIGS. 3a-3d provide graphs 240, 250, 260 and 270, respectively, showingthe induced charge Q on the pixelated anode 212 by the various chargeclouds 218, 220 and 222 shown in FIG. 3, respectively, as a function ofthe time t.

FIG. 3a schematically illustrates, in conjunction with FIG. 3, graph 240showing the induced charge Q on the pixelated anode 212 by charge clouds218, 218 a, and 218 b as a function of the time t. Segment 242 in graph240 relates to trajectory 232 (see FIG. 3) along which charge 218 moves.Charge cloud 218 induces charge Q on the pixelated anode 212 untilcharge cloud 218 is split into charge clouds 218 a and 218 b at point219.

Segment 244 in graph 240 relates to trajectories 224 and 226 (see FIG.3) along which charges 218 a and 218 b move from point 219, at whichpoint charge 218 is spit, to pixelated anodes 212 and 214, respectively.Charge 218 a induces charge on the pixelated anode 212 as a collectedcharge, and charge 218 b induces charge on the pixelated anode 212 as anon-collected charge moving away from the pixelated anode 212. Sincecharge 218 b moves away from the pixelated anode 212, charge 218 binduces negative charge on the pixelated anode 212, which causes thetotal induced charge Q on pixel 212 to drop down as shown in segment 244of graph 240. Segment 244 in graph 240 relates to the situation aftercharges 218 a and 218 b are already collected by pixelated anodes 212and 214, respectively. In this situation, the charge Q on the pixelatedanode 212 is stabilized at the value related to charge 218 a collectedby the pixelated anode 212.

With continued reference to FIG. 3, charge cloud 220 is formed byabsorbing a photon in the detector 210 near the cathode 208 of thedetector 210. The charge cloud 220 moves along trajectory 228 and towardthe pixelated anode 214 to be collected by the pixelated anode 214. FIG.3b schematically illustrates, in conjunction with FIG. 3, graph 250showing the induced charge Q on the collecting pixelated anode 214 bycharge cloud 220 as a function of time t. Segment 252 in graph 240relates to trajectory 228 (see FIG. 3) along which charge 220 moves.Charge cloud 220 induces charge Q on the collecting (or primary)pixelated anode 214 until it is collected by the pixelated anode 214 asis shown by segment 252 of graph 250. Segment 254 of graph 240 relatesto the situation after charge 220 is already collected by the pixelatedanode 214. In this situation, the charge Q on the pixelated anode 214 isstabilized at the value related to charge 220 collected by the pixelatedanode 214.

FIG. 3c schematically illustrates graph 260 showing the induced charge Qon the pixelated anode 212 versus time t produced by the charge 220collected by the primary pixelated anode 214. Graph 260 includes segment262 in which the induced charge Q increases (as discussed above) for thepositive integrated induced charge in region (I) of FIGS. 1 and 2.Segment 264 in graph 260 shows the induced charge Q decreasing (asdiscussed above) for the negative integrated induced charge in region(II) of FIGS. 1 and 2. From graph 260 of FIG. 3c it may be seen that theamplitude of the induced charge on the non-collecting pixelated anode isrelatively small, much smaller than the amplitude of the collectedsignal shown in graph 250 of FIG. 3b . This means that the non-collectedsignal may have poor SNR which may cause a relatively larger error inderiving the position of the event inside the physical primary pixel.

FIG. 3d provides an illustration of graph 270 showing the induced chargeQ on the pixelated anode 216 versus time t produced by charge 222collected by the primary pixelated anode 214. Graph 270 includes segment272 in which the induced charge Q increases (as discussed above) for thepositive integrated induced charge in region (I) of FIGS. 1 and 2.Segment 274 of graph 270 shows the induced charge Q decreasing (asdiscussed above) for the negative integrated induced charge in region(II) of FIGS. 1 and 2. As seen in FIG. 3d , the amplitude of the inducedsignal on the non-collecting pixelated anode in graph 270 issignificantly larger than that depicted in graph 260 of FIG. 3c . Thisis due to the difference in the relative positions of the trajectoriesof charge clouds 220 and 222 with respect to their non-collectingpixelated anodes 212 and 216 on which charge clouds induce theircharges, respectively, while being collected by primary pixelated anode214.

It may be noted that the trajectory 228 of cloud 220 is far away fromthe pixelated anode 212. Accordingly, the induced signal on thepixelated anode 212, by cloud 220, is relatively small as illustrated bygraph 260 of FIG. 3c . Unlike trajectory 228 of cloud 220, however,trajectory 230 of cloud 222 is relatively close and immediately underthe pixelated anode 216 where the electrical field of the weightingpotential of the pixelated anode 216 is strong. Accordingly, the inducedsignal on the pixelated anode 216, by cloud 222, is large as illustratedby graph 270 of FIG. 3 d.

It may further be noted that charge cloud 222 can move from the cathode208 to the pixelated anode 214 along trajectory 230 without beingcollected by the pixelated anode 216 even though most of trajectory 230is under the pixelated anode 216, because, in the illustrated example,the pixelated anode 216 has a potential (V-ΔV) that is lower than thepotential V of the pixelated anode 214. Accordingly, charge cloud 222 isattracted to the pixelated anode 214 rather than to the pixelated anode216 due to the higher potential of the pixelated anode 214.

It may be noted that in the case of FIG. 3d , the induced charge ishigher than that for FIG. 3c , and accordingly has better SNR resultingin more accurate position derivation of the primary event inside theprimary pixel 214. The principle of biasing the non-collecting anodeswith a potential that is lower than the potential of the collectinganodes for enhancing the induced signal on the non-collecting anodes isillustrative of various embodiments described below. However, in variousembodiments discussed herein specific anode geometry techniques areemployed to provide higher induced non-collected charges.

For example, FIGS. 4a-4c provide a schematic top view, a schematic sidesectional view, and a schematic end sectional view of an anodeunit-structure 300 according to various embodiments. The anodeunit-structure 300 is configured to enhance the amplitude of thenon-collected signal on the non-collecting anodes. In variousembodiments, the anode unit-structure 300 uses a bias voltageconfiguration that is similar in various respects to the one shown inFIG. 3, in which the bias voltage on the non-collecting anodes is lowerthan the bias voltage on the collecting anodes. Generally, in variousembodiments, as discussed in more detail below, the anode unit-structure300 includes two grids interleaved together. Each grid has two segmentsor regions, including a first segment or region that has exposed linesof metal strips (e.g., metal strips applied directly on thesemiconductor of the detector), and a second segment or region thatincludes isolated metal strips buried in electrically isolatingmaterial, with at least a portion of the electrically isolating materialforming an insulating layer located between the metal strips and thesemiconductor of the detector. The detector under the first segment orregion accordingly may be at a higher bias voltage than the detectorunder the second segment or region, with the first segment or regionutilized as a collecting anode, and the second segment or regionutilized as a non-collecting anode. In various embodiments, plural anodeunit-structures (or portions thereof) are joined to form an anode cell,with the anode cell used as a pixelated anode in a grid of pixelatedanodes.

FIG. 4a provides a plan view of an anode unit-structure 300. The anodeunit-structure 300 includes metal anode strips 302 electricallyconnected by a metal base strip 304 to form a fork-like structure 301with the anode strips 302. The depicted anode strips 302 have a length Lcontaining two segments. The first segment has a length L₁ and is anexposed segment 310 that is applied directly on semiconductor plate 306(shown in FIGS. 4a and 4c ) from which detector 308 (shown in FIG. 4c )is made. The second segment has a length L₂, and is a buried segment 312shown by broken lines. The buried segment 312 is buried (or interposed)between two insulating layers 314 and 316 shown in FIGS. 4a and 4c . Theinsulating layers 314, 316 have length L₃.

The electrically insulating layer 314 in various embodiments is applieddirectly on the semiconductor plate 306 of the detector 308, and theanode strips 302, in segment 310, are deposited directly on thesemiconductor plate 306 and deposited on layer 314 in segment 312. Theanode strips 302 may be deposited as segments 312 which are covered byan additional insulating layer 316 to form a buried strip 312 that issurrounded by the insulating layer 314 and the insulating layer 316 asshown in FIG. 4c and also shown in FIG. 4a . It may be noted that theinsulating layers 314, 316 may be made of, by way of example, positiveor negative photoresistors, Polyimid, polymers, insulating sticky tapes,or other insulating materials that may be applied on the semiconductorplate 306. Various techniques that may be used to apply the insulatinglayers include, for example, photolithographic techniques, painting,brushing, spraying, or taping. As shown in FIG. 4a , the depictedinsulating layers 314, 316 have a length L₃, which is larger than thelength L₂ of the segments 312. The longer lengths of the insulatinglayers helps ensure that the segments 312 are surrounded by insulatingmaterials from all sides except for the side where the segments areconnected to the segments 310.

In addition to the fork-like structure 301 (which includes the anodestrips 302, the connecting strip or base strip 304, the exposed segments310, and the buried segments 312) and the electrically insulating layers314 and 316, the anode unit-structure 300 includes fork-like structure330 having a mirror symmetry with the fork-like structure 301. Thefork-like structure 330 includes corresponding anode strips 322,connecting strip 328, exposed segments 324, buried segments 326, andelectrically insulating layers 318, 320 (see FIGS. 4a and 4b ). Thesegments and regions of the two grids (a first grid formed by the firstfork-like structure 301 and a second grid formed by the second fork-likestructure 330) are arranged such that where the first grid has a regionwith exposed strips, the second grid has buried or insulated strips, andvice versa. As seen in FIG. 4a , the exposed segments 310 of the firstfork-like structure 301 are adjacent to (or disposed in openingsbetween) the buried segments 326 of the second fork-like structure 330,and the buried segments 312 of the first fork-like structure 301 areadjacent to (or disposed in openings between) the exposed segments 324of the second fork-like structure 330. It may be noted that thefork-like structures are examples of grids, and that other shapes ofgrids may be used in various alternate embodiments.

It may be noted that FIG. 4b shows a cross-section of the buried strip326 surrounded by electrically insulating layers 318 and 320 from allsides except where the buried strip 326 is connected to the exposedstrip 324, with the cross-section of the buried strip 326 having mirrorsymmetry to the cross-section of the buried strip 312 surrounded byelectrically insulating layers 314 and 316 from all sides except whereit is connected to exposed strip 310. It may also be noted that whilethe side sectional view of FIG. 4c shows strips 312 that are buried byor interposed between insulating layers 314 and 316, that strips 326 areburied by or interposed between insulating layers 318 and 320 on theother side of the anode unit-structure 300, where the strips 310 areexposed. It may further be noted that, in various embodiments, thedetector 308 is a pixelated detector having pixilated anodes made ofanode cells, with each anode cell including one or more anodeunit-structures 300.

In various embodiments, both fork-like structures 301 and 330 are biasedat the same potential V. The exposed segments 302 and 324 are applied ontop of the semiconductor plate 306 and accordingly the detectorunderneath segments 302 and 324 has potential V. In contrast, the buriedsegments 312 and 326 are coupled to the semiconductor plate 306 via aresistor-like and/or capacitor-like structure formed by the electricallyinsulating layers 314 and 318. Accordingly, all the DC voltage V,applied between cathode 331 and the anodes, is dropped on these resistorand or capacitor-like structures and the potential of the semiconductorunder buried segments 312 and 326 is much lower than V or may be evenclose to zero. Accordingly, the buried segments 312 and 326 act asnon-collecting electrodes, with the potential, on detector 308,underneath these segments is much lower than the potential, on detector308, underneath exposed segments 302 and 324 and may even be close tozero, and substantially lower than the potential V underneath theexposed segments 310 and 324.

As seen in FIG. 4a , the depicted anode unit-structure 300 includes tworegions. A first region along length L₁ contains exposed segments 310 ofthe fork-like structure (or grid) 301, which are collecting anodestrips, and buried segments 326 of the fork-like structure (or grid)330, which are non-collecting anode strips. Similarly, the second regionalong length L₂ contains exposed segments 324 of the fork-like structure(or grid) 330, which are collecting anode strips, and buried segments312 of the fork-like structure (or grid) 301, which are non-collectinganode strips. The length of the exposed segments 324 including theirconnecting strip 328 is L₄.

As best seen in FIG. 4b , a photon 332 is absorbed in the semiconductorplate 306 of the detector 308 and produces charge cloud 334. The chargecloud 334 moves along trajectory 336 from the cathode 331 toward theanode strips in the first region of the anode unit-structure 300. Eventhough photon 332 is absorbed under one of non-collecting buriedsegments 326 in the first region of anode unit-structure 300, as shownin FIG. 4a , it will be collected by one of collecting exposed segments310 in the first region of structure 300 (due to the higher potential ofthe exposed segments relative to the buried segments).

This process is similar to that illustrated in the end sectional view inFIG. 4c , where the photon 344 is absorbed in the semiconductor plate306 of the detector 308 under the non-collecting buried anode strip 312and produces charge clouded 346 that moves toward the collecting exposedanode strip 324 to be collected by the anode strip 324. This process isalso generally similar in respects to that shown by charge 222 andtrajectory 230 of FIG. 3, which results in enhanced inducednon-collected signal shown by graph 270 of FIG. 3d . As used herein, anenhanced induced non-collected signal, such as the one shown by graph270 of FIG. 3d , means a non-collected induced signal, such as the oneproduced by moving charges under the non-collecting anodes, that islarger than the induced non-collected signal, such as the one shown ingraph 260 of FIG. 3c , which is received from a primary event occurringat a primary pixel that is adjacent to and remote from thenon-collecting pixel on which the non-collected signal is measured.Accordingly, events absorbed in the first region of the anodeunit-structure 300 are collected by one of the exposed segments 310 ofthe first fork-like structure (or grid) 301 and produce enhancednon-collected signals on the non-collecting buried segments 326 of thesecond fork-like structure (or grid) 330.

Also, as shown in FIG. 4c , photon 338 is absorbed in the semiconductorplate 306 of the detector 308 and produces charge cloud 340 moving alongtrajectory 342 from the cathode 331 toward the anode strips in thesecond region of the anode unit-structure 300. Photon 338 is absorbedunder one of collecting exposed segments 324 of the grid 330 in thesecond region of the anode unit-structure 300, as shown in FIG. 4a , andis collected by one of the collecting exposed segments 324 in the secondregion of the anode unit-structure 300. The collected charge on thesegment 324 is fed into the input of CSA 325, which is the first stageof a pre-amp of an associated electronic channel in an ASIC. For theillustrated embodiment, the detector 308 includes many segments 324 andeach of them is coupled to a corresponding CSA like CSA 325. It may benoted that, for example, segments 324, such as, segments 324 in grid330, are electrically connected by strip 328 and may be coupled to asingle CSA, such as CSA 325.

This process is also illustrated by the end sectional view shown in FIG.4c where the photon 338 is absorbed in the semiconductor plate 306 ofthe detector 308 under the collecting exposed anode strip 324 of thegrid 330 and produces charge cloud 340 that moves toward the collectingexposed anode strip 324 to be collected by the exposed anode strip 324.Even though charge cloud 340 is produced under segment 324 as shown inFIG. 4a , and moves along trajectory 342 directly toward the collectingexposed segment 324 of the grid 330, the charge cloud 340 still movesunder the non-collecting buried segments 312 of the grid 301 and,accordingly, produces an enhanced non-collected signal on the segments312. Accordingly, events absorbed in the second region of the anodeunit-structure 300 are collected by one of exposed segments 324 of thegrid 330 and produce enhanced non-collected signals on thenon-collecting buried segments 312 of the grid 301.

In summary, as seen in FIGS. 4a-c , any event that is produced in thefirst region of the anode unit-structure 300 of the detector 308 willproduce a collected signal on the grid 301 and an enhanced non-collectedsignal on the grid 330. Similarly, any event that is produced in thesecond region of the anode unit-structure 300 of the detector 308 willproduce a collected signal on the grid 330 and an enhanced non-collectedsignal on the grid 301. As the anode unit-structure 300 includes bothcollecting and non-collecting portions, any pixelated anode includingone or more anode unit-structures 300 (or portions thereof) provides anexample of a pixelated anode that includes collecting and non-collectingportions.

FIGS. 5a-5d schematically illustrate example processing steps that maybe used to fabricate the detector 308 with anode unit-structures 300.FIGS. 5a-5d and FIGS. 4a-4c illustrate corresponding components andaspects. Accordingly, similar reference numerals will be used inconnection with FIGS. 4a-c and 5a -d.

FIG. 5a illustrates a schematic plan view of the anode unit-structure300 showing the electrical insulating layer 314 in the form of staggeredstrips. The insulating layer 314 may be made, for example, of positiveor negative photoresistors or polyimid applied on top of thesemiconductor plate 306 using photolithographic techniques.Alternatively, the insulating layer 314 may be made of a passivationlayer, or may be made of ZnS evaporated on the semiconductor plate 306via shadowing mask or shaped by photolithographic methods.

FIG. 5b schematically illustrated grids (or fork-like structures in theillustrated example) 301 and 330. The grids 301, 330 of the illustratedembodiment are made of metal anode strips partially evaporated on theelectrically insulating layer 314 as well as on the semiconductor plate306. The grids 301 and 330 are interleaved one inside the other (e.g.,with the fingers or strips of each grid extending adjacent one or morefingers or strips of the other grid). The particular shapes of the grids301 and 330 may be formed by photolithographic techniques or usingshadowing masks, for example. FIG. 5d provides an exploded view of thegrids 301 and 330. FIG. 5d is provided for clarity of illustrating theshapes of the grids. As seen in FIG. 5d , the grids 301 and 330 areshown as two separated grids that are illustrated individually withoutbeing interleaved in the other grid.

FIG. 5c provides a schematic top view of the anode unit-structure 300that shows the electrical insulating layer 316 in the form of staggeredstrips. The insulating layer 316 in various embodiments may be made ofpositive or negative photoresistors or polyimid partially applied on topof the grids 301 and 330 and partially applied on the semiconductorplate 306 using photolithographic techniques. The strips of theinsulating layer 314 (see FIG. 5a ) and the insulating layer 316 in theillustrated embodiment are wider than the strips of the grids 301 and330. Accordingly, the electrically insulating layers 314 and 316surround and encapsulate the strips of the grids 301 and 330 from allsides in the buried regions except for the side connecting between theexposed strips and the buried strips of the grids 301 and 330.Alternatively, for example, the layer 316 may be made of ZnS evaporatedpartially on the grids 301 and 306 and partially evaporated on thesemiconductor plate 306 via shadowing mask or shaped byphotolithographic methods.

FIG. 6 provides a schematic plan view of an anode unit-cell 400 thatincludes four anode unit-structures 402, 404, 406 and 408 marked byframes of broken lines. Each anode unit-structure 402, 404, 406, and 408may be generally similar in various aspects to the anode unit-structure300 discussed herein. As explained above in the descriptionsaccompanying FIGS. 4a-4c and 5a-5d , each one of the anodeunit-structures 402, 404, 406 and 408 contains two grids, grid 301 andgrid 330. In the unit-cell 400 all the grids 330 of the anodesunit-structures 402, 404, 406 and 408 are facing out. Further, the grids301 of the anode unit-structures 402, 404, 406 and 408 are electricallyconnected and may form one contact-layer containing multiple grids 301,as shown in FIG. 7. For example, the grids 301 are connected toelectronic channels of an ASIC when at least one electronic channel isconnected to the corresponding grids 301 of each one of the pixels. Theconnected grids 301 may be referred to as a pixelated anode.Accordingly, a pixelated anode including the grids 301 includes exposedregions 310 within a square foot print 390 (which may be defined by acollimator opening) and insulated regions 312 extending beyond thesquare footprint 390 (which corresponds to opening 426 of collimator 420shown in FIG. 7).

It may be noted that the grid 301 and the grid 330 in unit-structures300 of unit-cell 400 have rotational symmetry of 180°. According, theposition of grids 301 and 330 may be swapped such that all grids 330 ofthe anode unit-structures 402, 404, 406 and 408 are electricallyconnected and may form one contact-layer containing multiple grids 330and all the grids 301 of the anodes unit-structures 402, 404, 406 and408 are facing out. Similarly, groups of connected grids 330 may be inturn connected to electronic channels of an ASIC, with at least oneelectronic channel is connected to the corresponding grids 330 of eachone of the pixelated anodes (or connected groups of grids 330).

FIG. 7 provides a schematic top view of a radiation imaging detector308. The detector 308 includes a semiconductor plate (or substrate) 306,and also includes a collimator 420 having septa 422 along Y directionand septa 424 along X direction, with the septa 422, 424 illustrated bybroken lines. The septa 422 and septa 424 form collimating openings 426in the collimator 420. FIG. 7 schematically illustrates a similar anodeunit-cell 400 to that shown in FIG. 6, which includes four anodeunit-structures 402, 404, 406 and 408 in a configuration with all grids301 are electrically and geometrically combined together to form asingle layer 301 containing multiple grids 301. The four connected grids301 of FIG. 7 may be referred to as a pixelated anode 701. It may benoted that pixelated anode 701 includes the exposed portions within thecorresponding pixel 428, but not the buried portions within thecorresponding pixel 428. The pixelated anode 701 also includes theburied portions that extend from the pixel 428 into adjacent pixelsshown in FIG. 7.

It may be noted that for a particular grid 301, that grid 301 isinterleaved with a given grid 330 to form an anode unit-structure.However, due to the connection of the particular grid 301 with othergrids 301 and the connection of the given grid 330 with other grids 330,the grid 330 is part of an adjacent pixelated anode to the pixelatedanode that is formed with the grid 301. Accordingly, while two grids maycooperate to form an anode unit-structure, the two grids may be part ofseparate pixelated anodes in various embodiments. It may further benoted that each pixel may be understood as being composed of twoportions. The first portion of the pixel is the exposed portions, whichserve as the collecting part of the pixel or corresponding pixelatedanode. The second portion of the pixel is the buried portions of thegrids that serve as the non-collecting portions of the pixels that areadjacent to the collecting pixel.

The collimator 420 is disposed above the surface of the semiconductorplate 306 and close to the anode unit-cell 400. The opening 426 abovethe anode unit-cell 400 defines a pixel 428 of the detector 308. It maybe noted that for clarity and ease of illustration, only one anodeunit-cell 400 of the detector 308 is shown. However, in practice, thedetector 308 may include multiple anode unit-cells 400 as discussedherein.

The septa 422 and 424 are aligned along the borders between the exposedsegments 310 and 324 and buried segments 312 and 326 of the anodeunit-structures 402, 404, 406 and 408 (see also exposed segments 310 and324 and buried segments 312 and 326 of anodes unit-structure 300 ofFIGS. 4a-4c ). As mentioned above, the relative position between theopenings 426 of collimator 420 and the anode unit-cell 400 determinesthe location of the pixel 428 to be the area on the anode unit-cell 400that the opening 426 surrounds or contains. The pixel 428 includes theexposed segments of four grids 301 of anodes unit-structures 402, 404,406 and 408, which are interleaved with the buried segments of fourgrids 330 of anodes unit-structures 402, 404, 406 and 408. It may benoted that the buried portions or segments of the four grids 301 formingthe pixelated anode 701 extend beyond the opening 426, or outside of thepixel 428. Accordingly, portions of the pixelated anode 701 (e.g., theburied portions of the grids 301) extend beyond the pixel 428 associatedwith the pixelated anode 701, or beyond the pixel 428 where thepixelated anode 701 resides.

When an event (e.g., absorbed photon) is produced in the area underpixel 428, the charge of this event produces a collected induced signalon the combined grid 301 inside the pixel 428 and produces at least oneenhanced non-collected induced signal on one of the grids 330 havingnon-collecting buried portions inside pixel 428 and exposed portionslocated in one of the surrounding pixels 430, 432, 434 or 436 that areadjacent to pixel 428. For example, if the event is produced under thearea of anode unit-structure 404 inside pixel 428, there would be acollected signal on the combined grid 301 in the pixel 428 and anenhanced non-collected signal on the grid 330 inside adjacent pixel 430.Similarly, if the event is produced under the area of the anodeunit-structure 406 that is inside pixel 428, there would be a collectedsignal on the combined grid 301 in the pixel 428 and an enhancednon-collected signal on the grid 330 inside the pixel 432. Similarly, ifthe event is produced under the area of the anode unit-structure 408inside the pixel 428, there would be a collected signal on the combinedgrid 301 in the pixel 428 and an enhanced non-collected signal on thegrid 330 inside the pixel 434. Or if, the event is produced under thearea of anodes unit-structure 402 inside pixel 428, there would be acollected signal on combined grid 301 in pixel 428 and an enhancednon-collected signal on grid 330 inside pixel 436.

Accordingly, when a collected event is measured on a combined grid 301at pixel 428 and a simultaneously enhanced non-collected signal ismeasured on grid 330 in one of the pixels 430, 432 434 or 436, it meansthat the event location is within the area of a quarter of pixel 428,which is the area of one of anode unit-structures 402, 404, 406 or 408,inside pixel 428, in which the enhanced non-collected signal is measuredon grid 330 at a pixel adjacent to pixel 428.

Accordingly, the location of the event inside the pixel 428 may be foundwith a spatial resolution that is equal to a quarter of the area of thepixel 428. The specific quarter inside pixel 428 in which the eventoccurs may be identified by the simultaneous collected signal andenhanced non-collected signals in the pixel 428 and a pixel adjacent topixel 428, respectively. Further, the quarter of the pixel 428 in whichthe collected event occurs is included in the anode unit-structure thatis common to the pixel 428 and the adjacent pixel in which thesimultaneous enhanced non-collected signal is measured. It may be notedthat the above discussion relates to the collected signal at pixel 428and the enhanced non-collected signal at one of the pixels adjacent topixel 428 when the enhanced non-collected signal is the strongest signalmeasured out of all the signals at the pixels adjacent to pixel 428.Other adjacent non-collected signals measured at pixels adjacent topixel 428 may be used to apply weighted average of these signals forderiving sub-pixilation of each of the quarters, mentioned above, insidepixel 428.

Next, reference is made to FIGS. 8a and 8b . For clarity ofillustration, FIG. 8a schematically illustrates an enlarged part ofFIGS. 7 and 8 b. The arrow 458 indicates that the portion of FIG. 8bthat includes the pixel 428 is enlarged in FIG. 8a , and includes theanode unit-cell 400 that contains anode unit-structures 402, 404, 406and 408. The opening 426 of the collimator 420 is disposed above thepixel 428 and aligned with the pixel 428. The anode unit-structures 402,404, 406 and 408 have a common combined grid 301 having its exposedportions within the pixel 428 and its buried portions outside pixel 428in the pixels adjacent to pixel 428, along with grids 330 having theirexposed portions located outside of the pixel 428 and their buriedportions inside pixel 428. The pixel 428 is virtually divided, by brokenlines 462 and 464, into four virtual sub-pixels 450, 452, 454 and 456.As discussed above in connection with FIG. 7, the location of an eventsuch as event 460 in the sub-pixel 450 is identified by measuringsimultaneously a collected event in the pixel 428 and an enhancednon-collected event on grid 330 of the anode unit-structure 404 havingexposed segments in the pixel adjacent to pixel 428.

FIG. 8b schematically depicts a collimator 20 having nine openings 426,with various of the openings 426 located above the pixels 428, 430, 432,434 and 436. FIG. 8b shows multiple anode unit-structures 300 forminganode unit-cells 400, which are butted together to form, together withcollimator 420, a pixilated plane. Again, it may be noted that oneportion of a given anode unit-structure (or unit-cell) may form aportion of a first pixel or pixelated anode, while another portion ofthe same anode unit-structure (or unit-cell) may form a portion of adifferent pixel or pixelated anode.

In FIG. 8b , for ease of illustration, the unit-cells 400 are slightlyshifted from each other to create a small gap between them to allowvisualization of each of the anode unit-cells 400 individually. Inpractice, in various embodiments there are no such gaps between theanode unit-cells 400, the exposed parts of the grids 301 areelectrically connected, and the exposed parts of grids 330 areelectrically connected. As mentioned above, the grids 301 and 330 have asymmetry of 180°. Accordingly, the grids 330 and 301 are symmetricbetween adjacent pixels. Accordingly, pixels behave as if theircorresponding grids 301 (or 330) are electrically connected inside allthe pixels but not between pixelated anodes. It should be understoodthat even though there are no or very small gaps between the anodeunit-cells 400, there is no electrical connection between the grids 301and 330 of a given unit-structure or unit-cell.

In various embodiments, the anode unit-cells 400 are butted to eachother while their orientation ensures that only one anode unit-structure(e.g., anode unit-structures 402, 404, 406 and 408) is common to twoadjacent pixels. For example, adjacent pixels 428 and 430 share only oneanode unit-structure 404, adjacent pixels 428 and 436 share only oneanode unit-structure 402, adjacent pixels 428 and 434 share only oneanode unit-structure 408, and adjacent pixels 428 and 432 share only oneanode unit-structure 406. In such a situation, for example, event 460 inpixel 428 (see FIG. 8a ) will produce simultaneously a collected signalin pixel 428 and an enhanced non-collected signal in pixel 430 (see alsoFIG. 8b ) where the exposed segments of grids 330 of the anodeunit-structures are electrically connected.

Accordingly, when the collected event and the enhanced non-collectedevent appear simultaneously on pixels 428 and 430 of FIG. 8b , it meansthat the primary event occurred in the anode unit-structure 404 in thearea of the pixel 428, which is virtual sub-pixel 450 in FIG. 8a .Similarly, when a collected event and an enhanced non-collected eventappear simultaneously on pixels 428 and 432 of FIG. 8b , it means thatthe primary event occurred in the anode unit-structure 406 in the areaof pixel 428, which is virtual sub-pixel 452 in FIG. 8a . When thecollected event and the enhanced non-collected event appearsimultaneously on pixels 428 and 434 of FIG. 8b , respectively, it meansthat the primary event occurred in anode unit-structure 408 in the areaof pixel 428, which is virtual sub-pixel 454 in FIG. 8a . Also, when thecollected event and enhanced non-collected event appear simultaneouslyon pixels 428 and 436 of FIG. 8b , respectively, it means that theprimary event occurred in anode unit-structure 402 in the area of pixel428, which is virtual sub-pixel 456 in FIG. 8 a.

Accordingly, as discussed above, the location of every primary event maybe found and assigned into one of four virtual pixels to which thephysical pixel is divided into. The process is based on the simultaneousmeasurement of the collected signal and the enhanced non-collectedsignal in the primary pixel and the pixel adjacent to the primary pixel,respectively. The use of enhanced non-collected signals improves the SNRof the non-collected signals, thus allowing more accurate derivation ofthe location of the primary event and makes possible measurement ofsmall non-collected signals that without the enhancement of theiramplitude discussed herein may not be accurately detected.

FIG. 9a provides a schematic depiction of the butting of unit-cells 400on the semiconductor plate 306 of the detector 308 (not shown in FIG. 9a). The anode unit-cell 400 includes 4 anode unit-structures 402, 404,406 and 408. The orientation of the anode unit-structures 402, 404, 406and 408 are defined as the orientation of their grids 301 and 330.Accordingly, adjacent anode unit-structures are rotated at 90° relativeto each other, with each of the anode unit-structures 402, 404, 406, and408 having one corner located at point 403. It may be noted that thelongest dimension of the anode unit-structures 402, 404, 406 and 408 isin the direction defined as the orientation of the anodesunit-structures.

For ease and clarity of illustration for FIG. 9a , the anode unit-cells400 are shown butted together but with gaps between them. In practice invarious embodiments, these gaps do not exist but are shown for depictingthe relative positions between the unit-cells 400. In variousembodiments, the anode unit-cells 400 are butted with no rotationbetween them and the longest dimensions of the adjacent anodeunit-structures of different unit-cells 400 are oriented in the samedirection.

FIG. 9b schematically depicts a butting or joining of anode unit-cells400 similar to that shown in FIG. 9a . However, in FIG. 9b , they areshown without the gaps between the anode unit-cells 400 shown in FIG. 9a. FIG. 9b also shows the relative position between the unit-cells 400,their anode unit-structures 402, 404, 406 and 408 and a part ofcollimator 420 (shown in broken lines). It may be seen in FIG. 9b thatthe corners of the collimator 420 are located at the center of the areaformed by two adjacent anode unit-structures of two different unit-cells400 that are aligned along the same orientation. The relative positionbetween collimator 420 including its septa and anodes 400 is alsoillustrated by FIG. 7 and explained in the associated description.

FIG. 9c schematically depicts the butting or joining of the anodeunit-cells 400 over an area greater than the area shown in FIG. 9b andarranged to be bigger than the area of collimator 420. As can be seen inFIG. 9c , in order for the butted area of the anode unit-cells 400 tocover the whole area of collimator 420, the area of the anode unit-cells400 should be larger than the area of collimator 420 in the illustratedexample. As explained above in connection with FIGS. 7 and 8 b, eachopening of the collimator 420 defines a pixel. Each pixel includes partof four different anode unit-structures that are rotated at 90° relativeto each other. Further, two adjacent pixels share only one common anodeunit-structure such as one of anodes unit-structures 402, 404, 406 and408.

FIG. 10a schematically illustrates a unit-cell 400, FIG. 10bschematically illustrates the relative position between the unit-cell400 and a part of collimator 420 (illustrated by broken lines) with thearea under the opening 426 of the collimator 420 defining the pixel 428.FIG. 10c schematically illustrates the area of butted anode unit-cells400 as being equal to the area under collimator 420. As mentioned above,in order for the butted area of unit cells 400 to cover the whole areaof collimator 420, the butted area should be larger than the area ofcollimator 420. As a result, having the butted area of unit cells 400cover the same area as does the collimator 420 (or detector 308), anodeunit-cells 401 under the circumference or edge of the collimator 420should include only part of the anode unit-structures (whereas anodeunit-cell 400 includes the entirety of the correspondingunit-structures). Accordingly, the depicted anode unit-cells 401 includeless than four anodes unit-structures.

It may be noted that while collimator 420 appears above the anodeunit-cells 400, it is very close to the cathode of detector 308 whilethe anode unit-cells 400 are still under collimator 420 but, on theother plane of the semiconductor plate 306 facing away from thecollimator 420 in various embodiments. It may further be noted that, foreach pixel of the detector 308, the exposed segments of grids 301 or 330are electrically coupled to a Charge-Sensitive-Amplifier (CSA), which isthe pre-amplifier of the electronic channel that corresponding to thepixel.

With continued reference to FIGS. 7, 8 a, and 8 b, improvements to theintrinsic resolution of detector 308 will be discussed. The location ofan event, such as event 460 inside a virtual sub-pixel, such as virtualsub-pixel 450 in physical pixel 428, may be found.

As discussed above, the derivation of the event location within thesub-pixel may be accomplished using the primary event of the pixel andthe enhanced non-collected induced signal in the pixel adjacent to theprimary pixel. This method has the advantage of having an enhancednon-collected induced signal that is stronger than conventionalnon-collected induced signals derived from a pixel adjacent to theprimary pixel when the pixelated anodes are arranged in the conventionalstructure of pixelated anodes. On the other hand, both the primarysignal and the enhanced induced non-collected signal are insensitive tothe location of the event inside the sub-pixels. Accordingly, furtherinformation is needed for deriving the location of the event inside thesub-pixels.

The information used in the present discussion to derive the location ofthe event is the amplitudes of the non-collected induced signals fromthe anode unit-structures in the pixels adjacent to the primary pixelwhich do not contain the event. For example, the X, Y coordinates of thelocation of event 460 inside virtual sub-pixel 450 of physical pixel 428is derived by measuring the non-collected induced signals from anodeunit-structures 406 and 406 in pixels 432 and 436, respectively.

The coordinate X of event 460 in virtual sub-pixel 450 of physical pixel428 is given by:

$\begin{matrix}{X = {K_{X} \cdot {d(450)} \cdot \frac{I(406)}{I(428)}}} & {{Eq}.\mspace{14mu} (7)}\end{matrix}$

where X is the coordinate along the X axis which is measured from theboundary between the anode unit-structure 406 and the anodeunit-structure 404 into virtual sub-pixel 450, K_(X) is the proportionalcoefficient along the X axis, d(450) is the dimension of virtualsub-pixel 450, I(406) is the amplitude of the non-collected inducedsignal at the anode unit-structure 406 as measured by pixel 432, andI(428) is the amplitude of the collected signal at pixel 428. Themathematical term

$\frac{I(406)}{I(428)}$

is the normalized signal I(406) of the non-collected induced signal. Thenormalized signal I(406) may be derived using another mathematical term

$\frac{I(406)}{I(404)}$

when I(404) is the enhanced induced non-collected signal at the anodeunit-structure 404. It may be noted that the proportional coefficientalong the X axis K_(X) has different values for different normalizationof signal I(406).

Similarly, the coordinate Y of event 460 in virtual sub-pixel 450 ofphysical pixel 428 is given by:

$\begin{matrix}{Y = {K_{Y} \cdot {d(450)} \cdot \frac{I(402)}{I(428)}}} & {{Eq}.\mspace{14mu} ( {7a} )}\end{matrix}$

where Y is the coordinate along the Y axis which is measured from theboundary between the anode unit-structure 402 and the anodeunit-structure 404 into virtual sub-pixel 450, K_(Y) is the proportionalcoefficient along the Y axis, d(450) is the dimension of virtualsub-pixel 450, I(402) is the amplitude of non-collected induced signalat the anode unit-structure 402 as measured by pixel 436, and I(428) isthe amplitude of the collected signal at pixel 428. The mathematicalterm

$\frac{I(402)}{I(428)}$

is the normalized signal I(402) of the non-collected induced signal. Thenormalized signal I(402) may be derived using another mathematical term

$\frac{I(402)}{I(404)}$

when I(404) is the enhanced induced non-collected signal at anodesunit-structure 404. It may be noted that the proportional coefficientK_(Y) has different value for different normalization of signal I(402).

FIG. 11 is a schematic illustration of an electronic channel inside anASIC used in various embodiments. The electronic channel includes twobranches. One branch includes a conventional shaper, and the otherbranch includes a fast shaper. This design facilitates distinguishingbetween collected and non-collected signals and thus is useful todetermine the type of the measured signal on the different pixels. Amore complete description of the design of FIG. 11 is provided in U.S.patent application Ser. No. 15/860,325 entitled “Systems and Methods forCollecting Radiation Detection”, filed Jan. 2, 2018, which is herebyincorporated by reference in its entirety.

FIG. 12 provides a schematic side view of a radiation detector assembly1200 in accordance with various embodiments. FIG. 13 provides a top viewof a semiconductor detector 1210 of the radiation detector assembly1200, and FIG. 14 provides an enlarged plan view of the radiationdetector assembly 1200. As seen in FIG. 12, the radiation detectorassembly 1200 includes a semiconductor detector 1210, a collimator 1230,and a processing unit 1220. The semiconductor detector 1210 has asurface 1212 (see FIG. 13) on which plural pixelated anodes 1214 (seeFIG. 13) are disposed. A cathode (not shown in FIG. 12) may be disposedon a surface opposite the surface 1212 on which the pixelated anodes1214 are disposed. For example, a single cathode may be deposited on onesurface with the pixelated anodes disposed on an opposite surface.Generally, when radiation (e.g., one or more photons) impacts thesemiconductor detector 1210, the semiconductor detector 1210 generateselectrical signals corresponding to the radiation being absorbed in thevolume of detector 1210.

The semiconductor detector 1210 in various embodiments may beconstructed using different materials, such as semiconductor materials,including Cadmium Zinc Telluride (CdZnTe), often referred to as CZT,Cadmium Telluride (CdTe), and Silicon (Si), among others. The detector1210 may be configured for use with, for example, nuclear medicine (NM)imaging systems, positron emission tomography (PET) imaging systems,and/or single photon emission computed tomography (SPECT) imagingsystems.

Referring to FIG. 14, the collimator 1230 is disposed above the surface1212 of FIG. 12, and includes openings 1232 configured to directradiation to the semiconductor detector 1210. Each opening 1232 definesa corresponding pixel 1234.

In the illustrated embodiment of FIGS. 12 and 13, each pixelated anode1214 generates different signals depending on the lateral location(e.g., in the X, Y directions) of where a photon is absorbed in thevolume of detector 1210 under the surface 1212. It may be noted that thepixelated anodes 1214 in FIGS. 12 and 13 are depicted as being square orrectangular shaped; however, in various embodiments the pixelated anodesmay take on other shapes, including those discussed in connection withFIGS. 4-10. For example, each pixelated anode 1214 generates a primaryor collected signal responsive to the absorption of a photon in thevolume of detector 1210 under or corresponding to the particularpixelated anode 1214 (e.g., under an associated or corresponding openingof the collimator 1230 through which the photon penetrates into thedetector volume. The volumes of detector 1210 under corresponding pixelsmay be defined as voxels (not shown). For each pixelated anode 1214,detector 1210 has the corresponding voxel. The absorption of a photon bya certain voxel corresponding to a particular pixelated anode 1214 alsoresults in an induced charge that may be detected by pixels 1214adjacent to or surrounding the particular pixelated anode 1214 thatreceives the photon. The charge detected by an adjacent or surroundingpixel may be referred to herein as a non-collected charge, and result ina non-collected or secondary signal. A primary signal may includeinformation regarding photon energy (e.g., a distribution across a rangeof energy levels) as well as location information corresponding to theparticular pixelated anode 1214 at which a photon penetrates via thesurface 1212 and is absorbed in the corresponding voxel.

As best seen in FIG. 14, the collimator 1230 includes openings 1232.Each pixelated anode 1214 of the illustrated example includes a firstportion 1250 and a second portion 1260. The first portion 1250 islocated in a first opening 1232 a, while the second portion 1260 islocated in a second opening 1232 b. Accordingly, different portions ofthe pixelated anode 1214 are located in different pixels.

In some embodiments, the first portion 1250 is a collecting portionconfigured to collect a primary charge responsive to reception of aphoton by the pixelated anode 1214, while the second portion 1260 is anon-collecting portion configured to collect a secondary chargeresponsive to reception of a photon by an adjacent pixelated anode(e.g., a pixelated anode having a collecting portion disposed in thecollimator opening 1232 b in which the second or non-collecting portion1260 of the pixelated anode 1214 is disposed). Accordingly, thecollecting portion may be disposed in the opening 1232 a above thepixelated anode 1214, and the non-collecting portion may be disposedwithin the opening 1232 b that is above an adjacent pixelated anode. Theexposed and buried portions of FIGS. 4-10 provide further examples ofcollecting and non-collecting portions that may be disposed in adjacentcollimator openings or pixels.

For example, in various embodiments, the pixelated anodes 1214 may bemade of anode unit-cells (e.g., anode unit-cell 400) that in turn aremade of anode unit-structures (e.g., anode unit-structure 300). Asdiscussed above, each anode unit-structure may include a first portionand a second portion that form portions of different pixelated anodes1214. For example, the exposed portions of an anode unit-structure 300may form a part of a first pixelated anode, while the buried orinsulated portions from a part of a second pixelated anode adjacent tothe first pixelated anode. As discussed in connection with FIGS. 4-10,for example, the anode unit-structures may include interleavedcollecting and non-collecting grids. For instance, the non-collectinggrids may include anode strips interposed between insulating layers asdiscussed in connection with FIGS. 4-5. Further, the grids may includeanode strips (e.g., anode strips 302) that extend from a base strip(e.g., base strip 304) to form a fork-like structure.

Alternatively, the openings 1232 of the collimator 1230 may be offsetfrom the pixelated anodes 1214. For example, FIG. 18 depicts acollimator 1400 having septa 1410 forming openings 1412, shown in solidlines. The collimator 1400 may be used in conjunction with pixelatedanodes 1420 having borders 1422 shown in dashed lines. In theillustrated embodiment, the pixelated anodes 1420 and collimatoropenings 1412 having a similar pitch (or width), but are offset by ½ ofa pitch, so that the pixelated anode borders 1422 pass through thecenter of the collimator openings 1412. Other amounts of offset orvariances in collimator and pixelated anode pitch may be employed invarious embodiments.

The arrangement of FIG. 18 allows the increase of the inducednon-collected signal. For example, when the collimator 1400 isregistered to the pixelated anodes 1420, the center of the pixel matchesthe center of the collimator hole. It may be noted that the center ofthe pixelated anode 1420 is the area with the highest exposure rate.Further, the distance between the center of the pixel and theneighboring pixels is at a maximum when the event hits the center of thepixel. Accordingly, to increase the induce signal detected by theneighboring pixels, the collimator 1400 may be moved by a half pitch inthe lateral directions to have the center of the pixel blocked by septa1410 of the collimator 1400 (it may be noted the center is the pixelarea with the lowest subpixel accuracy because it is the portion of thepixel farthest away from neighboring pixels). Accordingly, by shiftingthe collimator position with respect to pixelated anodes, the portionsof the pixels with the lowest subpixel accuracy may be aligned with thesepta 902, and to have the center of the collimator openings 1412 matchthe corners of the pixelated anodes 1420.

Returning to FIGS. 12-14, each pixelated anode 1214 may have associatedtherewith one or more electronics channels configured to provide theprimary and secondary signals to one or more aspects of the processingunit 1220 in cooperation with the pixelated anodes. In some embodiments,all or a portion of each electronics channel may be disposed on thedetector 1210. Alternatively or additionally, all or a portion of eachelectronics channel may be housed externally to the detector 1210, forexample as part of the processing unit 1220, which may be or include anApplication Specific Integration Circuit (ASIC). The electronicschannels may be configured to provide the primary and secondary signalsto one or more aspects of the processing unit 1220 while discardingother signals. For example, in some embodiments, each electronicschannel includes a threshold discriminator. The threshold discriminatormay allow signals exceeding a threshold level to be transmitted whilepreventing or inhibiting transmission of signals that do not exceed athreshold level. Generally, the threshold level is set low enough toreliably capture the secondary signals, while still being set highenough to exclude lower strength signals, for example due to noise. Itmay be noted that, because the secondary signals may be relatively lowin strength, the electronics utilized are preferably low noiseelectronics to reduce or eliminate noise that is not eliminated by thethreshold level. In some embodiments, each electronic channel includes apeak-and-hold unit to store electrical signal energy, and may alsoinclude a readout mechanism. For example, the electronic channel mayinclude a request-acknowledge mechanism that allows the peak-and-holdenergy and pixel location for each channel to be read out individually.Further, in some embodiments, the processing unit 1220 or otherprocessor may control the signal threshold level and therequest-acknowledge mechanism.

In the illustrated embodiment, the processing unit 1220 is operablycoupled to the pixelated anodes 1214, and is configured to acquireprimary signals (for collected charges) and secondary signals (fornon-collected charges). The processing unit 1220 also determines alocation for the reception of the photon using the primary signal andthe at least one secondary signal. For example, as discussed inconnection with FIGS. 7, 8 a, and 8 b, the processing unit 1220 may beconfigured to determine the location of an event (reception of a photon)based on a simultaneous (e.g., within a narrow, predetermined timerange) measurement of a collected signal by a primary pixelated anodeand an enhanced non-collected signal in a secondary pixel adjacent tothe primary pixel. In various embodiments, the processing unit 1220 isconfigured to reconstruct an image using acquired counts of events.

The processing unit 1220 in various embodiments is configured to furtherdetermine sub-pixel locations using one or more techniques discussed inU.S. patent application Ser. No. 14/724,022, entitled “Systems andMethod for Charge-Sharing Identification and Correction Using a SinglePixel,” filed 28 May 2015 (“the 022 application); U.S. patentapplication Ser. No. 15/280,640, entitled “Systems and Methods forSub-Pixel Location Determination,” filed 29 Sep. 2016 (“the 640application”); and U.S. patent application Ser. No. 14/627,436, entitled“Systems and Methods for Improving Energy Resolution by Sub-Pixel EnergyCalibration,” filed 20 Feb. 2015 (“the 436 application). The subjectmatter of each of the 022 application, the 640 application, and the 436application are incorporated by reference in its entirety.

In various embodiments the processing unit 1220 includes processingcircuitry configured to perform one or more tasks, functions, or stepsdiscussed herein. It may be noted that “processing unit” as used hereinis not intended to necessarily be limited to a single processor orcomputer. For example, the processing unit 1220 may include multipleprocessors, ASIC's, FPGA's, and/or computers, which may be integrated ina common housing or unit, or which may distributed among various unitsor housings. It may be noted that operations performed by the processingunit 1220 (e.g., operations corresponding to process flows or methodsdiscussed herein, or aspects thereof) may be sufficiently complex thatthe operations may not be performed by a human being within a reasonabletime period. For example, the determination of values of collected andnon-collected charges, and/or the determination of DOI's and/orsub-pixel locations based on the collected and/or non-collected chargeswithin the time constraints associated with such signals may rely on orutilize computations that may not be completed by a person within areasonable time period.

The depicted processing unit 1220 includes a memory 1222. The memory1222 may include one or more computer readable storage media. The memory1222, for example, may store acquired emission information, image datacorresponding to images generated, results of intermediate processingsteps, or the like. Further, the process flows and/or flowchartsdiscussed herein (or aspects thereof) may represent one or more sets ofinstructions that are stored in the memory 1222 for direction ofoperations of the radiation detection assembly 1200.

FIG. 15 provides a flowchart of a method 1500 in accordance with variousembodiments. The method 1500, for example, may employ or be performed bystructures or aspects of various embodiments (e.g., systems and/ormethods and/or process flows) discussed herein. In various embodiments,certain steps may be omitted or added, certain steps may be combined,certain steps may be performed concurrently, certain steps may be splitinto multiple steps, certain steps may be performed in a differentorder, or certain steps or series of steps may be re-performed in aniterative fashion. In various embodiments, portions, aspects, and/orvariations of the method 1500 may be able to be used as one or morealgorithms to direct hardware (e.g., one or more aspects of theprocessing unit 1220) to perform one or more operations describedherein.

At 1502, a semiconductor substrate (e.g., semiconductor plate 306) isprovided. At 1504, anode unit-structures (e.g., anode unit-structure300) are provided on the semiconductor substrate. Each anodeunit-structure includes anode strips configured to receive electricalcharge responsive to absorption of a photon by the semiconductor. Forexample, in various embodiments, the anode unit-structure includescollecting and non-collecting portions, which may be arranged in aninterleaved arrangement as discussed herein.

Various techniques may be employed for forming the anode unit-structuresand/or disposing the anode unit-structures on the semiconductorsubstrate. The anode unit-structures may be disposed on a surface of thesemiconductor substrate that is opposite a cathode. The collectingportions may be formed by direct deposition or joining of anelectrically conductive material (e.g., metal) on a surface of thesemiconductor substrate. Insulating layers in conjunction with aconductive or metal layer may be utilized to form the non-collectingportions. For example, in the illustrated embodiment, at 1506, aninsulating layer is provided on the semiconductor substrate. At 1508, ananode strip is provided on top of the insulating layer, with theinsulating interposed between the anode strip and the semiconductorsurface. At 1510, an additional insulating layer is provided on top ofthe anode strip, with the anode strip interposed between the twoinsulating layers. (See also FIGS. 5a-5d and related discussion.)

At 1512, plural anode unit-structures are arranged into correspondinganode unit-cells, with each anode unit-cell including at least two anodeunit-structures. For example, in the depicted example, at 1514, fourgrids (e.g., grids 301) of four corresponding anode unit-structures areconnected to form a corresponding pixelated anode. It may be noted thatthe anode unit-cell formed by the connection of the anodeunit-structures may include insulated or buried non-collecting portionsthat are electrically separated from the pixelated anode formed byconnecting the grids, and that extend into adjacent pixels.

At 1516, the anode unit-cells are arranged into pixelated anodes. Thepixelated anodes may be connected to corresponding electronic channelsfor processing and/or transmission of signals that may be used todetermined counts corresponding to received photons. At least a firstportion and second portion of each anode unit-structure form portions ofdifferent pixelated anodes. (See also FIG. 7 and related discussion.)

FIG. 16 is a schematic illustration of a NM imaging system 1000 having aplurality of imaging detector head assemblies mounted on a gantry (whichmay be mounted, for example, in rows, in an iris shape, or otherconfigurations, such as a configuration in which the movable detectorcarriers 1016 are aligned radially toward the patient-body 1010). Inparticular, a plurality of imaging detectors 1002 are mounted to agantry 1004. In the illustrated embodiment, the imaging detectors 1002are configured as two separate detector arrays 1006 and 1008 coupled tothe gantry 1004 above and below a subject 1010 (e.g., a patient), asviewed in FIG. 16. The detector arrays 1006 and 1008 may be coupleddirectly to the gantry 1004, or may be coupled via support members 1012to the gantry 1004 to allow movement of the entire arrays 1006 and/or1008 relative to the gantry 1004 (e.g., transverse translating movementin the left or right direction as viewed by arrow T in FIG. 16).Additionally, each of the imaging detectors 1002 includes a detectorunit 1014, at least some of which are mounted to a movable detectorcarrier 1016 (e.g., a support arm or actuator that may be driven by amotor to cause movement thereof) that extends from the gantry 1004. Insome embodiments, the detector carriers 1016 allow movement of thedetector units 1014 towards and away from the subject 1010, such aslinearly. Thus, in the illustrated embodiment the detector arrays 1006and 1008 are mounted in parallel above and below the subject 1010 andallow linear movement of the detector units 1014 in one direction(indicated by the arrow L), illustrated as perpendicular to the supportmember 1012 (that are coupled generally horizontally on the gantry1004). However, other configurations and orientations are possible asdescribed herein. It should be noted that the movable detector carrier1016 may be any type of support that allows movement of the detectorunits 1014 relative to the support member 1012 and/or gantry 1004, whichin various embodiments allows the detector units 1014 to move linearlytowards and away from the support member 1012.

Each of the imaging detectors 1002 in various embodiments is smallerthan a conventional whole body or general purpose imaging detector. Aconventional imaging detector may be large enough to image most or allof a width of a patient's body at one time and may have a diameter or alarger dimension of approximately 50 cm or more. In contrast, each ofthe imaging detectors 1002 may include one or more detector units 1014coupled to a respective detector carrier 1016 and having dimensions of,for example, 4 cm to 20 cm and may be formed of Cadmium Zinc Telluride(CZT) tiles or modules. For example, each of the detector units 1014 maybe 8×8 cm in size and be composed of a plurality of CZT pixelatedmodules (not shown). For example, each module may be 4×4 cm in size andhave 16×16=256 pixels. In some embodiments, each detector unit 1014includes a plurality of modules, such as an array of 1×7 modules.However, different configurations and array sizes are contemplatedincluding, for example, detector units 1014 having multiple rows ofmodules.

It should be understood that the imaging detectors 1002 may be differentsizes and/or shapes with respect to each other, such as square,rectangular, circular or other shape. An actual field of view (FOV) ofeach of the imaging detectors 1002 may be directly proportional to thesize and shape of the respective imaging detector.

The gantry 1004 may be formed with an aperture 1018 (e.g., opening orbore) therethrough as illustrated. A patient table 1020, such as apatient bed, is configured with a support mechanism (not shown) tosupport and carry the subject 1010 in one or more of a plurality ofviewing positions within the aperture 1018 and relative to the imagingdetectors 1002. Alternatively, the gantry 1004 may comprise a pluralityof gantry segments (not shown), each of which may independently move asupport member 1012 or one or more of the imaging detectors 1002.

The gantry 1004 may also be configured in other shapes, such as a “C”,“H” and “L”, for example, and may be rotatable about the subject 1010.For example, the gantry 1004 may be formed as a closed ring or circle,or as an open arc or arch which allows the subject 1010 to be easilyaccessed while imaging and facilitates loading and unloading of thesubject 1010, as well as reducing claustrophobia in some subjects 1010.

Additional imaging detectors (not shown) may be positioned to form rowsof detector arrays or an arc or ring around the subject 1010. Bypositioning multiple imaging detectors 1002 at multiple positions withrespect to the subject 1010, such as along an imaging axis (e.g., headto toe direction of the subject 1010) image data specific for a largerFOV may be acquired more quickly.

Each of the imaging detectors 1002 has a radiation detection face, whichis directed towards the subject 1010 or a region of interest within thesubject.

In various embodiments, multi-bore collimators may be constructed to beregistered with pixels of the detector units 1014, which in oneembodiment are CZT detectors. However, other materials may be used.Registered collimation may improve spatial resolution by forcing photonsgoing through one bore to be collected primarily by one pixel.Additionally, registered collimation may improve sensitivity and energyresponse of pixelated detectors as detector area near the edges of apixel or in-between two adjacent pixels may have reduced sensitivity ordecreased energy resolution or other performance degradation. Havingcollimator septa directly above the edges of pixels reduces the chanceof a photon impinging at these degraded-performance locations, withoutdecreasing the overall probability of a photon passing through thecollimator.

A controller unit 1030 may control the movement and positioning of thepatient table 1020, imaging detectors 1002 (which may be configured asone or more arms), gantry 1004 and/or the collimators 1022 (that movewith the imaging detectors 1002 in various embodiments, being coupledthereto). A range of motion before or during an acquisition, or betweendifferent image acquisitions, is set to maintain the actual FOV of eachof the imaging detectors 1002 directed, for example, towards or “aimedat” a particular area or region of the subject 1010 or along the entiresubject 1010. The motion may be a combined or complex motion in multipledirections simultaneously, concurrently, or sequentially as described inmore detail herein.

The controller unit 1030 may have a gantry motor controller 1032, tablecontroller 1034, detector controller 1036, pivot controller 1038, andcollimator controller 1040. The controllers 1030, 1032, 1034, 1036,1038, 1040 may be automatically commanded by a processing unit 1050,manually controlled by an operator, or a combination thereof. The gantrymotor controller 1032 may move the imaging detectors 1002 with respectto the subject 1010, for example, individually, in segments or subsets,or simultaneously in a fixed relationship to one another. For example,in some embodiments, the gantry controller 1032 may cause the imagingdetectors 1002 and/or support members 1012 to move relative to or rotateabout the subject 1010, which may include motion of less than or up to180 degrees (or more).

The table controller 1034 may move the patient table 1020 to positionthe subject 1010 relative to the imaging detectors 1002. The patienttable 1020 may be moved in up-down directions, in-out directions, andright-left directions, for example. The detector controller 1036 maycontrol movement of each of the imaging detectors 1002 to move togetheras a group or individually as described in more detail herein. Thedetector controller 1036 also may control movement of the imagingdetectors 1002 in some embodiments to move closer to and farther from asurface of the subject 1010, such as by controlling translating movementof the detector carriers 1016 linearly towards or away from the subject1010 (e.g., sliding or telescoping movement). Optionally, the detectorcontroller 1036 may control movement of the detector carriers 1016 toallow movement of the detector array 1006 or 1008. For example, thedetector controller 1036 may control lateral movement of the detectorcarriers 1016 illustrated by the T arrow (and shown as left and right asviewed in FIG. 14). In various embodiments, the detector controller 1036may control the detector carriers 1016 or the support members 1012 tomove in different lateral directions. Detector controller 1036 maycontrol the swiveling motion of detectors 1002 together with theircollimators 1022.

The pivot controller 1038 may control pivoting or rotating movement ofthe detector units 1014 at ends of the detector carriers 1016 and/orpivoting or rotating movement of the detector carrier 1016. For example,one or more of the detector units 1014 or detector carriers 1016 may berotated about at least one axis to view the subject 1010 from aplurality of angular orientations to acquire, for example, 3D image datain a 3D SPECT or 3D imaging mode of operation. The collimator controller1040 may adjust a position of an adjustable collimator, such as acollimator with adjustable strips (or vanes) or adjustable pinhole(s).

It should be noted that motion of one or more imaging detectors 1002 maybe in directions other than strictly axially or radially, and motions inseveral motion directions may be used in various embodiment. Therefore,the term “motion controller” may be used to indicate a collective namefor all motion controllers. It should be noted that the variouscontrollers may be combined, for example, the detector controller 1036and pivot controller 1038 may be combined to provide the differentmovements described herein.

Prior to acquiring an image of the subject 1010 or a portion of thesubject 1010, the imaging detectors 1002, gantry 1004, patient table1020 and/or collimators 1022 may be adjusted, such as to first orinitial imaging positions, as well as subsequent imaging positions. Theimaging detectors 1002 may each be positioned to image a portion of thesubject 1010. Alternatively, for example in a case of a small sizesubject 1010, one or more of the imaging detectors 1002 may not be usedto acquire data, such as the imaging detectors 1002 at ends of thedetector arrays 1006 and 1008, which as illustrated in FIG. 14 are in aretracted position away from the subject 1010. Positioning may beaccomplished manually by the operator and/or automatically, which mayinclude using, for example, image information such as other imagesacquired before the current acquisition, such as by another imagingmodality such as X-ray Computed Tomography (CT), MRI, X-Ray, PET orultrasound. In some embodiments, the additional information forpositioning, such as the other images, may be acquired by the samesystem, such as in a hybrid system (e.g., a SPECT/CT system).Additionally, the detector units 1014 may be configured to acquirenon-NM data, such as x-ray CT data. In some embodiments, amulti-modality imaging system may be provided, for example, to allowperforming NM or SPECT imaging, as well as x-ray CT imaging, which mayinclude a dual-modality or gantry design as described in more detailherein.

After the imaging detectors 1002, gantry 1004, patient table 1020,and/or collimators 1022 are positioned, one or more images, such asthree-dimensional (3D) SPECT images are acquired using one or more ofthe imaging detectors 1002, which may include using a combined motionthat reduces or minimizes spacing between detector units 1014. The imagedata acquired by each imaging detector 1002 may be combined andreconstructed into a composite image or 3D images in variousembodiments.

In one embodiment, at least one of detector arrays 1006 and/or 1008,gantry 1004, patient table 1020, and/or collimators 1022 are moved afterbeing initially positioned, which includes individual movement of one ormore of the detector units 1014 (e.g., combined lateral and pivotingmovement) together with the swiveling motion of detectors 1002. Forexample, at least one of detector arrays 1006 and/or 1008 may be movedlaterally while pivoted. Thus, in various embodiments, a plurality ofsmall sized detectors, such as the detector units 1014 may be used for3D imaging, such as when moving or sweeping the detector units 1014 incombination with other movements.

In various embodiments, a data acquisition system (DAS) 1060 receiveselectrical signal data produced by the imaging detectors 1002 andconverts this data into digital signals for subsequent processing.However, in various embodiments, digital signals are generated by theimaging detectors 1002. An image reconstruction device 1062 (which maybe a processing device or computer) and a data storage device 1064 maybe provided in addition to the processing unit 1050. It should be notedthat one or more functions related to one or more of data acquisition,motion control, data processing and image reconstruction may beaccomplished through hardware, software and/or by shared processingresources, which may be located within or near the imaging system 1000,or may be located remotely. Additionally, a user input device 1066 maybe provided to receive user inputs (e.g., control commands), as well asa display 1068 for displaying images. DAS 1060 receives the acquiredimages from detectors 1002 together with the corresponding lateral,vertical, rotational and swiveling coordinates of gantry 1004, supportmembers 1012, detector units 1014, detector carriers 1016, and detectors1002 for accurate reconstruction of an image including 3D images andtheir slices.

It may be noted that the embodiment of FIG. 16 may be understood as alinear arrangement of detector heads (e.g., utilizing detector unitsarranged in a row and extending parallel to one another. In otherembodiments, a radial design may be employed. Radial designs, forexample, may provide additional advantages in terms of efficientlyimaging smaller objects, such as limbs, heads, or infants. FIG. 17provides a schematic view of a nuclear medicine (NM) multi-head imagingsystem 1100 in accordance with various embodiments. Generally, theimaging system 1100 is configured to acquire imaging information (e.g.,photon counts) from an object to be imaged (e.g., a human patient) thathas been administered a radiopharmaceutical. The depicted imaging system1100 includes a gantry 1110 having a bore 1112 therethrough, pluralradiation detector head assemblies 1115, and a processing unit 1120.

The gantry 1110 defines the bore 1112. The bore 1112 is configured toaccept an object to be imaged (e.g., a human patient or portionthereof). As seen in FIG. 15, plural radiation detector head assemblies1115 are mounted to the gantry 1110. In the illustrated embodiment, eachradiation detector head assembly 1115 includes an arm 1114 and a head1116. The arm 1114 is configured to articulate the head 1116 radiallytoward and/or away from a center of the bore 1112 (and/or in otherdirections), and the head 1116 includes at least one detector, with thehead 1116 disposed at a radially inward end of the arm 1114 andconfigured to pivot to provide a range of positions from which imaginginformation is acquired.

The detector of the head 1116, for example, may be a semiconductordetector. For example, a semiconductor detector various embodiments maybe constructed using different materials, such as semiconductormaterials, including Cadmium Zinc Telluride (CdZnTe), often referred toas CZT, Cadmium Telluride (CdTe), and Silicon (Si), among others. Thedetector may be configured for use with, for example, nuclear medicine(NM) imaging systems, positron emission tomography (PET) imagingsystems, and/or single photon emission computed tomography (SPECT)imaging systems.

In various embodiments, the detector may include an array of pixelatedanodes, and may generate different signals depending on the location ofwhere a photon is absorbed in the volume of the detector under a surfaceif the detector. The volumes of the detector under the pixelated anodesare defined as voxels. For each pixelated anode, the detector has acorresponding voxel. The absorption of photons by certain voxelscorresponding to particular pixelated anodes results in chargesgenerated that may be counted. The counts may be correlated toparticular locations and used to reconstruct an image.

In various embodiments, each detector head assembly 1115 may define acorresponding view that is oriented toward the center of the bore 1112.Each detector head assembly 1115 in the illustrated embodiment isconfigured to acquire imaging information over a sweep rangecorresponding to the view of the given detector unit. Additional detailsregarding examples of systems with detector units disposed radiallyaround a bore may be found in U.S. patent application Ser. No.14/788,180, filed 30 Jun. 2015, entitled “Systems and Methods ForDynamic Scanning With Multi-Head Camera,” the subject matter of which isincorporated by reference in its entirety.

The processing unit 1120 includes memory 1122. The imaging system 1100is shown as including a single processing unit 1120; however, the blockfor the processing unit 1120 may be understood as representing one ormore processors that may be distributed or remote from each other. Thedepicted processing unit 1120 includes processing circuitry configuredto perform one or more tasks, functions, or steps discussed herein. Itmay be noted that “processing unit” as used herein is not intended tonecessarily be limited to a single processor or computer. For example,the processing unit 1120 may include multiple processors and/orcomputers, which may be integrated in a common housing or unit, or whichmay distributed among various units or housings.

Generally, various aspects (e.g., programmed modules) of the processingunit 1120 act individually or cooperatively with other aspects toperform one or more aspects of the methods, steps, or processesdiscussed herein. In the depicted embodiment, the memory 1122 includes atangible, non-transitory computer readable medium having stored thereoninstructions for performing one or more aspects of the methods, steps,or processes discussed herein.

It may be noted that various apparatuses and methods disclosed aboveenhance non-collected induced signals measured at pixels adjacent to apixel that includes a primary collected event. It may further be notedthat the charge collection efficiency of the primary signal and theenhancement of the non-collected induced signals are both proportionalto the respective areas of the collecting electrodes and thenon-collecting electrodes included in each pixel. Accordingly, invarious embodiments, it is desirable to have the areas of the collectingand non-collecting electrodes in each pixel as large as possible.However, as the total area available within each pixel is limited,increasing the area of the collecting electrodes will reduce the area ofthe non-collecting electrodes, or increasing the area of thenon-collecting electrodes will reduce the area of the collectingelectrodes.

Accordingly, in various embodiments, the areas of the collecting andnon-collecting electrodes are varied, adjusted, or selected to providean improved or optimal balance between charge collection efficiency(e.g., as provided by the collecting electrodes) and enhancement ofnon-collected signals. Additionally or alternatively, variousembodiments provide improved accuracy or efficiency of electricalconnection points (e.g., gluing or soldering bumps) for each pixel forconnection to an electrical board (e.g., an analog-front-end (AFE)electronic board).

FIGS. 19A-19D schematically illustrate an anode unit-structure 1200 inaccordance with various embodiments. It may be noted that the anodeunit-structure 1200 may be generally similar to or incorporate variousaspects of anode unit-structure 300 discussed in connection with FIGS.5A-5D, or other examples discussed herein. For example, the anodeunit-structure 1200 may be used in connection with anode unit-cell 400discussed in connection with FIG. 6, and/or with systems discussed inconnection with FIGS. 12, 16, and 17. As seen in FIGS. 19A-19D, theanode unit-structure 1200 includes a grid 1201 and a grid 1230 that haveinterleaving strips or segments.

The anode unit-structure 1200, however, differs from the anodeunit-structure 300 of FIGS. 5A-5D in various respects. For example, thegrid 1201 includes collecting strips 1205 that are relatively wider (orwider than the non-collecting strips), and non-collecting strips 1203that are relatively narrower (or narrower than the collecting strips).Also, the grid 1230 includes collecting strips 1235 that are relativelywider and non-collecting strips 1233 that are relatively narrower.

Accordingly, the collecting strips 1205 and 1235 of the collectingelectrodes of grids 1201 and 1230, respectively, are wider and have arelatively larger area (e.g., larger than the non-collecting strips, orlarger than the area for collecting strips in examples where thecollecting and non-collecting strips are the same size) providing highercharge collection efficiency for the primary signal. On the other hand,the non-collecting segments 1203 and 1233 of the non-collectingelectrodes of grids 1201 and 1230, respectively, are narrower and have arelatively smaller area, resulting in reduced enhancement ofnon-collected induced signals.

Insulating layers (e.g., including insulating strips), as discussedherein, may be used in connection with the anode unit-structure 1200.For example, as seen in FIGS. 19A and 19B, lower insulating strips 1214may be deposited directly on a semiconductor plate. As seen in FIG. 19B,the non-collecting strips 1203, 1233 may be deposited on top of thelower insulating strips 1214. Then, as seen in FIG. 19C, additionalinsulating strips 1216 may be deposited on top of the non-collectingstrips to form buried non-collecting strips. It may be noted that, forease and clarity of illustration, relatively large gaps are shownbetween adjacent strips in FIGS. 19A-19D. However, the collecting stripsmay be made wider (and the insulating strips narrower) to reduce the gapsize and provide for more area for the collecting strips.

A number of anode unit-structures 1200 may be joined to form pluralpixelated anodes disposed on a surface of a semiconductor, as discussedherein. (See, e.g., FIGS. 6-10 and related discussion.) For example, apixelated anode may be understood as having a first portion 1250 that isconfigured as a collecting portion 1252, and a second portion 1260 thatis configured as a non-collecting portion 1262. The first portion 1250and second portion 1260 may be disposed in different openings of anassociated collimator (e.g., with the second portion 1260 disposedwithin an opening of the collimator above a corresponding collectingportion of a pixelated anode that is adjacent to the pixelated anodethat includes the first portion 1250). For example, the collectingstrips 1205 of the grid 1201 located in a first pixel, and thecollecting strips 1235 of the grid 1230 located in an adjacent pixelalong with the non-collecting strips 1203 of the grid 1201. As seen inthe illustrated example, the collecting portion 1252 defines acollecting area 1254. For example, the collecting portion 1252 includesthe collecting strips 1205 and the collecting area 1254 includes the sumof the areas of the individual collecting strips 1205. Also, thenon-collecting portion 1262 defines a non-collecting area 1264. Forexample, the non-collecting portion 1260 includes the non-collectingstrips 1203, and the non-collecting area 1264 includes the sum of theareas of the individual non-collecting strips 1203. (It may be notedthat any given pixelated anode may include more than one grid ofcollecting and non-collecting strips, for example as depicted anddiscussed in connection with FIGS. 6-10.) As seen in the illustratedexample, the collecting area 1254 and the non-collecting area 1264 aredifferent sizes. Because the collecting strips are wider than thenon-collecting strips (while both are generally the same length andthere are the same numbers of each), the collecting area 1254 is largerthan the non-collecting area 1264.

Accordingly, FIGS. 19A-19D depict an anode unit-structure 1200 in whichthe charge collection efficiency is improved and the enhancement ofnon-collected induced signals is relatively reduced by varying the areasof the collecting and non-collecting portions (e.g., varying the widthof the collecting strips and non-collecting strips to be relativelywider and narrower, respectively). Accordingly, a balance or tradeoffbetween charge collection on the one hand, and enhancement ofnon-collected signals on the other hand, may be achieved by varying therespective areas of the collecting and non-collecting portions.

In other embodiments, charge collection may be relatively reduced toprovide improved enhancement of non-collected signals. For example,FIGS. 20A-20D schematically illustrate an anode unit-structure 1300 inaccordance with various embodiments, in which primary charge collectionis relatively reduced to provide improved enhancement of non-collectedsignals. It may be noted that the anode unit-structure 1300 may begenerally similar to or incorporate various aspects of anodeunit-structure 300 discussed in connection with FIGS. 5A-5D, or otherexamples discussed herein. For example, the anode unit-structure 1300may be used in connection with anode unit-cell 400 discussed inconnection with FIG. 6, and/or with systems discussed in connection withFIGS. 12, 16, and 17. As seen in FIGS. 20A-20D, the anode unit-structure1300 includes a grid 1301 and a grid 1330 that have interleaving stripsor segments.

The anode unit-structure 1300, however, differs from the anodeunit-structure 300 of FIGS. 5A-5D in various respects. For example, thegrid 1301 includes collecting strips 1305 that are relatively narrower,and non-collecting strips 1303 that are relatively wider. Also, the grid1330 includes collecting strips 1335 that are relatively narrower andnon-collecting strips 1333 that are relatively wider.

Accordingly, the collecting strips 1305 and 1335 of the collectingelectrodes of grids 1301 and 1330, respectively, are narrower and have arelatively smaller area, providing lower charge collection efficiencyfor the primary signal. On the other hand, the non-collecting segments1303 and 1333 of the non-collecting electrodes of grids 1301 and 1330,respectively, are wider and have a relatively larger area, resulting inincreased enhancement of non-collected induced signals.

Insulating layers (e.g., including insulating strips), as discussedherein, may be used in connection with the anode unit-structure 1300.For example, as seen in FIGS. 20A and 20B, lower insulating strips 1314may be deposited directly on a semiconductor plate. As seen in FIG. 20B,the non-collecting strips 1303, 1333 may be deposited on top of thelower insulating strips 1314. Then, as seen in FIG. 19C, additionalinsulating strips 1316 may be deposited on top of the non-collectingstrips to form buried non-collecting strips. It may be noted that, forease and clarity of illustration, relatively large gaps are shownbetween adjacent strips in FIGS. 19A-19D. However, the non-collectingstrips (and associated insulating strips) may be made wider to reducethe gap size and provide for more area for the non-collecting strips.

It may further be noted that a number of anode unit-structures 1300 maybe joined to form plural pixelated anodes disposed on a surface of asemiconductor, as discussed herein. (See, e.g., FIGS. 6-10 and relateddiscussion.) For example, a pixelated anode may be understood as havinga first portion 1350 that is configured as a collecting portion 1352,and a second portion 1360 that is configured as a non-collecting portion1362. The first portion 1350 and second portion 1360 may be disposed indifferent openings of an associated collimator (e.g., with the secondportion 1360 disposed within an opening of the collimator above acorresponding collecting portion of a pixelated anode that is adjacentto the pixelated anode that includes the first portion 1350).

As seen in the example depicted in FIGS. 20A-20D, the collecting portion1352 defines a collecting area 1354. For example, the collecting portion1352 includes the collecting strips 1305 and the collecting area 1354includes the sum of the areas of the individual collecting strips 1305.Also, the non-collecting portion 1362 defines a non-collecting area1364. For example, the non-collecting portion 1360 includes thenon-collecting strips 1303, and the non-collecting area 1364 includesthe sum of the areas of the individual non-collecting strips 1303. (Itmay be noted that any given pixelated anode may include more than onegrid of collecting and non-collecting strips, for example as depictedand discussed in connection with FIGS. 6-10.) As seen in the illustratedexample, the collecting area 1354 and the non-collecting area 1364 aredifferent sizes. Because the collecting strips are narrower than thenon-collecting strips (while both are generally the same length andthere are the same numbers of each), the collecting area 1354 is smallerthan the non-collecting area 1364.

Accordingly, FIGS. 20A-20D depict an anode unit-structure 1300 in whichthe charge collection efficiency is relatively reduced and theenhancement of non-collected induced signals is relatively improved byvarying the areas of the collecting and non-collecting portions (e.g.,varying the width of the collecting strips and non-collecting strips tobe relatively narrower and wider, respectively). Accordingly, a balanceor tradeoff between charge collection on the one hand, and enhancementof non-collected signals on the other hand, may be achieved by varyingthe respective areas of the collecting and non-collecting portions.

As discussed in connection with FIG. 6, for example, various embodimentsinclude anode unit-cells that include anode unit-structures. FIGS.21A-21C provide schematic illustrations of an anode unit-cell 1400. Itmay be noted that the anode unit-cell 1400 may be generally similar toor incorporate various aspects of anode unit-cell 400 discussed inconnection with FIG. 6, and/or be used in connection with systemsdiscussed in connection with FIGS. 12, 16, and 17. The depictedunit-cell 1400 includes collecting portion 1470 and non-collectingportion 1460. FIG. 21A is a schematic top view of the anode unit-cell1400, FIG. 21B is a schematic top view of the collecting portion 1460,and FIG. 21C is a schematic top view of the non-collecting portion 1470.The collecting portion 1460 is disposed within a collimator openingdefining pixel 1402, while the non-collecting portion 1470 is disposedwithin one or more adjacent collimator openings defining adjacentpixels. For example, the collecting portion 1460 of grid 1201 mayinclude collecting strips 1205 and pad 1450, while the non-collectingportion 1470 may include non-collecting strips 1203 as seen in FIG. 20B.

The depicted unit-cell 1400 includes anode-units 1200 having grids 1201and 1230 that include collecting strips 1205 and 1235, respectively, andnon-collecting strips 1203 and 1233, respectively. As with the examplediscussed in connection with FIGS. 19A-19D, the collecting strips 1205,1235 are wider than the non-collecting strips 1203, 1233. The grid 1201depicted in FIGS. 21A and B, however, also includes a pad 1450 defininga central collecting area 1451. (It may be noted that lengths of one ormore of collecting or non-collecting strips of the grids 1201, 1230 maybe adjusted to accommodate the central collecting area 1451, and/or theshape or total number of strips and/or orientations of strips of thegrids may be adjusted to accommodate the central collecting area 1451.)The central collecting area 1451 is sized to accommodate solder or gluefor connecting the unit-cell 1400 to a circuit board, and providing asufficient distances from the electrical connection to insulate thenon-collecting strips 1203, 1233 from an electrical connection betweenthe pad 1450 and the circuit board. The pad 1450 and central collectingarea 1451 also help provide for accurate alignment when mountingunit-cells to a circuit board.

It may be noted that, in connection with FIGS. 21A-21C, collectingstrips are shown as wider than non-collecting strips; however, in otherembodiments the non-collecting strips may be wider (e.g., the anodeunit-cell 1400 may include anode unit-structures 1300, or otherwisegenerally similar aspects to those discussed in connection with FIGS.20A-20D), or the collecting strips and non-collecting strips may besimilarly sized.

As discussed above, the pad 1450 may be used to electrically couple thecorresponding unit-cell 1400 with a circuit board (e.g., for receivingprimary signals corresponding to the pixel 1402 in which the pad 1450 isdisposed and/or induced signals from adjacent pixels. FIG. 22 depicts asectional view of a system 2200 including a circuit board 2210 and aunit-cell 1400. The unit-cell 1400 is disposed on a surface 2252 of asemiconductor detector 2250, with the pad 1450 electrically coupled to aconnection point 2211 of the circuit board 2210 (e.g., via soldering).An insulating layer 2260 is provided underneath a non-collecting portion2270 (e.g., a non-collecting strip from an adjacent unit-cell). However,because all electrical connections between the unit-cell 1400 and thecircuit board 2210 are achieved between connection point 2211 and pad1450, and the connection is a sufficient distance from thenon-collecting portions to avoid shorts, an insulating layer between thenon-collecting portion 2270 and the circuit board 2210 is not required,and the illustrated example is devoid of an insulating layer between thenon-collecting portion 2270 and the circuit board 2210.

FIG. 23 provides a flowchart of a method 2300 in accordance with variousembodiments. The method 2300, for example, may employ or be performed bystructures or aspects of various embodiments (e.g., systems and/ormethods and/or process flows) discussed herein. For example, the method2300 may incorporate one or more aspects of the method 1500, and/or oneor more aspects of the method 2300 may be used in connection with themethod 1500. In various embodiments, certain steps may be omitted oradded, certain steps may be combined, certain steps may be performedconcurrently, certain steps may be split into multiple steps, certainsteps may be performed in a different order, or certain steps or seriesof steps may be re-performed in an iterative fashion. In variousembodiments, portions, aspects, and/or variations of the method 2300 maybe able to be used as one or more algorithms to direct hardware (e.g.,one or more aspects of the processing unit 1220) to perform one or moreoperations described herein.

At 2302, a semiconductor substrate (e.g., semiconductor plate 306) isprovided. At 2304, anode unit-cells (e.g., unit-cells 400) are disposedon a surface of the semiconductor substrate. It may be noted that one ormore unit-structures (e.g., unit-structures 1200 or 1300) may be used toform unit-cells. Each anode unit-cell includes anode portions thatinclude at least one collecting portion and one non-collecting portion.

At 2306 the anode unit cells are arranged into pixelated anodes (e.g.,by arranging the unit cells on the surface of the semiconductor as theyare disposed on the surface). The collecting portion of each anode unitcell includes a central collecting area (e.g., central collecting area1451). For each anode unit cell, at least one of the collecting portionsand at least one of the non-collecting portions for portions ofdifferent pixels (e.g., the collecting portion forms a portion of agiven pixel, and the non-collecting portion forms a portion of one ormore adjacent pixels). It may be noted that in various embodiments thecollecting portion may define a collecting area, and the non-collectingportion may define a non-collecting area, with the collecting area andnon-collecting area having different sizes from each other, as discussedherein.

One or more insulating layers may also be provided on the semiconductorsurface. For example, at 2308 of the depicted embodiment, an insulatinglayer is provided that is interposed between the non-collecting portionand the surface of the semiconductor on which the anodes are disposed.In some embodiments, no insulating layer may be provided on top of thenon-collecting portion or interposed between the non-collecting portionand a circuit board.

At 2310, a collimator is disposed above the surface on which the anodeportions are provided (e.g., above a cathode surface that is disposedopposite and above the anode portions). Each pixel of the semiconductordetector is defined by an opening of the collimator disposed above theunit cells.

At 2312, a circuit board (e.g., circuit board 2210 or printed circuitboard) is disposed opposite the surface above which the collimator isdisposed, or adjacent to the surface on which the anode portions aredisposed), and a central collecting area of each anode unit cell iselectrically coupled to the circuit board.

It should be noted that the various embodiments may be implemented inhardware, software or a combination thereof. The various embodimentsand/or components, for example, the modules, or components andcontrollers therein, also may be implemented as part of one or morecomputers or processors. The computer or processor may include acomputing device, an input device, a display unit and an interface, forexample, for accessing the Internet. The computer or processor mayinclude a microprocessor. The microprocessor may be connected to acommunication bus. The computer or processor may also include a memory.The memory may include Random Access Memory (RAM) and Read Only Memory(ROM). The computer or processor further may include a storage device,which may be a hard disk drive or a removable storage drive such as asolid-state drive, optical disk drive, and the like. The storage devicemay also be other similar means for loading computer programs or otherinstructions into the computer or processor.

As used herein, the term “computer” or “module” may include anyprocessor-based or microprocessor-based system including systems usingmicrocontrollers, reduced instruction set computers (RISC), ASICs, logiccircuits, and any other circuit or processor capable of executing thefunctions described herein. The above examples are exemplary only, andare thus not intended to limit in any way the definition and/or meaningof the term “computer”.

The computer or processor executes a set of instructions that are storedin one or more storage elements, in order to process input data. Thestorage elements may also store data or other information as desired orneeded. The storage element may be in the form of an information sourceor a physical memory element within a processing machine.

The set of instructions may include various commands that instruct thecomputer or processor as a processing machine to perform specificoperations such as the methods and processes of the various embodiments.The set of instructions may be in the form of a software program. Thesoftware may be in various forms such as system software or applicationsoftware and which may be embodied as a tangible and non-transitorycomputer readable medium. Further, the software may be in the form of acollection of separate programs or modules, a program module within alarger program or a portion of a program module. The software also mayinclude modular programming in the form of object-oriented programming.The processing of input data by the processing machine may be inresponse to operator commands, or in response to results of previousprocessing, or in response to a request made by another processingmachine.

As used herein, a structure, limitation, or element that is “configuredto” perform a task or operation is particularly structurally formed,constructed, or adapted in a manner corresponding to the task oroperation. For purposes of clarity and the avoidance of doubt, an objectthat is merely capable of being modified to perform the task oroperation is not “configured to” perform the task or operation as usedherein. Instead, the use of “configured to” as used herein denotesstructural adaptations or characteristics, and denotes structuralrequirements of any structure, limitation, or element that is describedas being “configured to” perform the task or operation. For example, aprocessing unit, processor, or computer that is “configured to” performa task or operation may be understood as being particularly structuredto perform the task or operation (e.g., having one or more programs orinstructions stored thereon or used in conjunction therewith tailored orintended to perform the task or operation, and/or having an arrangementof processing circuitry tailored or intended to perform the task oroperation). For the purposes of clarity and the avoidance of doubt, ageneral purpose computer (which may become “configured to” perform thetask or operation if appropriately programmed) is not “configured to”perform a task or operation unless or until specifically programmed orstructurally modified to perform the task or operation.

As used herein, the terms “software” and “firmware” are interchangeable,and include any computer program stored in memory for execution by acomputer, including RAM memory, ROM memory, EPROM memory, EEPROM memory,and non-volatile RAM (NVRAM) memory. The above memory types areexemplary only, and are thus not limiting as to the types of memoryusable for storage of a computer program.

It is to be understood that the above description is intended to beillustrative, and not restrictive. For example, the above-describedembodiments (and/or aspects thereof) may be used in combination witheach other. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the variousembodiments without departing from their scope. While the dimensions andtypes of materials described herein are intended to define theparameters of the various embodiments, they are by no means limiting andare merely exemplary. Many other embodiments will be apparent to thoseof skill in the art upon reviewing the above description. The scope ofthe various embodiments should, therefore, be determined with referenceto the appended claims, along with the full scope of equivalents towhich such claims are entitled. In the appended claims, the terms“including” and “in which” are used as the plain-English equivalents ofthe respective terms “comprising” and “wherein.” Moreover, in thefollowing claims, the terms “first,” “second,” and “third,” etc. areused merely as labels, and are not intended to impose numericalrequirements on their objects. Further, the limitations of the followingclaims are not written in means-plus-function format and are notintended to be interpreted based on 35 U.S.C. § 112(f) unless and untilsuch claim limitations expressly use the phrase “means for” followed bya statement of function void of further structure.

This written description uses examples to disclose the variousembodiments, including the best mode, and also to enable any personskilled in the art to practice the various embodiments, including makingand using any devices or systems and performing any incorporatedmethods. The patentable scope of the various embodiments is defined bythe claims, and may include other examples that occur to those skilledin the art. Such other examples are intended to be within the scope ofthe claims if the examples have structural elements that do not differfrom the literal language of the claims, or the examples includeequivalent structural elements with insubstantial differences from theliteral languages of the claims.

What is claimed is:
 1. A radiation detector assembly comprising: asemiconductor detector having a surface; a collimator disposed above thesurface, the collimator having openings defining pixels; pluralpixelated anodes disposed on the surface, each pixelated anodeconfigured to generate a primary signal responsive to reception of aphoton by the pixelated anode and to generate at least one secondarysignal responsive to an induced charge caused by reception of a photonby at least one surrounding anode, wherein each pixelated anode includesa first portion and a second portion located in different openings ofthe collimator, wherein each of the pixelated anodes comprises acollecting portion configured to collect a primary charge responsive toreception of a photon by the pixelated anode, and a non-collectingportion configured to collect a secondary charge responsive to receptionof a photon by an adjacent pixelated anode, wherein the first portion isconfigured as the collecting portion, and the second portion isconfigured as the non-collecting portion and is disposed within anopening of the collimator above a collecting portion of an adjacentpixelated anode, wherein the collecting portion defines a collectingarea and the non-collecting portion defines a non-collecting area, andwherein the collecting area and the non-collecting area have differentsizes from each other; and at least one processor operably coupled tothe pixelated anodes, the at least one processor configured to: acquirea primary signal from one of the pixelated anodes responsive toreception of a photon by the one of the anodes; acquire at least onesecondary signal from at least one neighboring pixelated anode of theone of the pixelated anodes responsive to an induced charge caused bythe reception of the photon by the one of the anodes; and determine alocation for the reception of the photon using the primary signal andthe at least one secondary signal.
 2. The radiation detector assembly ofclaim 1, wherein the collecting area is larger than the non-collectingarea.
 3. The radiation detector assembly of claim 2, wherein thecollecting area includes collecting strips and the non-collecting areaincludes non-collecting strips, the non-collecting strips having atleast one insulating layer associated therewith, wherein the collectingstrips are wider than the non-collecting strips.
 4. The radiationdetector assembly of claim 2, wherein the collecting area includes acentral collecting area.
 5. The radiation detector assembly of claim 4,further comprising a printed circuit board disposed opposite the surfaceof the semiconductor detector above which the collimator is disposed,wherein the collecting area is electrically coupled to the printedcircuit board.
 6. The radiation detector assembly of claim 1, whereinthe non-collecting area is larger than the collecting area.
 7. Theradiation detector assembly of claim 6, wherein the collecting areaincludes collecting strips and the non-collecting area includesnon-collecting strips, the non-collecting strips having at least oneinsulating layer associated therewith, wherein the non-collecting stripsare wider than the collecting strips.
 8. A radiation detector assemblycomprising: a semiconductor detector having a surface; a collimatordisposed above the surface, the collimator having openings definingpixels; plural pixelated anodes disposed on the surface, each pixelatedanode configured to generate a primary signal responsive to reception ofa photon by the pixelated anode and to generate at least one secondarysignal responsive to an induced charge caused by reception of a photonby at least one surrounding anode, wherein each pixelated anode includesa first portion and a second portion located in different openings ofthe collimator, wherein each of the pixelated anodes comprises acollecting portion configured to collect a primary charge responsive toreception of a photon by the pixelated anode, and a non-collectingportion configured to collect a secondary charge responsive to receptionof a photon by an adjacent pixelated anode, wherein the first portion isconfigured as the collecting portion, and the second portion isconfigured as the non-collecting portion and is disposed within anopening of the collimator above a collecting portion of an adjacentpixelated anode, wherein the collecting area includes a centralcollecting area; and at least one processor operably coupled to thepixelated anodes, the at least one processor configured to: acquire aprimary signal from one of the pixelated anodes responsive to receptionof a photon by the one of the anodes; acquire at least one secondarysignal from at least one neighboring pixelated anode of the one of thepixelated anodes responsive to an induced charge caused by the receptionof the photon by the one of the anodes; and determine a location for thereception of the photon using the primary signal and the at least onesecondary signal.
 9. The radiation detector assembly of claim 8, furthercomprising a printed circuit board disposed opposite the surface of thesemiconductor detector above which the collimator is disposed, whereinthe central collecting area is electrically coupled to the printedcircuit board.
 10. The radiation detector assembly of claim 9, furthercomprising an insulating layer disposed on the surface of thesemiconductor detector on which the anodes are disposed, the insulatinglayer beneath the non-collecting portion.
 11. The radiation detectorassembly of claim 10, wherein the radiation detector assembly is devoidof an insulating layer between the non-collecting portion and theprinted circuit board.
 12. The radiation detector assembly of claim 8,wherein the collecting portion defines a collecting area and thenon-collecting portion defines a non-collecting area, and wherein thecollecting area and the non-collecting area have different sizes fromeach other.
 13. The radiation detector assembly of claim 12, wherein thecollecting area is larger than the non-collecting area.
 14. Theradiation detector assembly of claim 13, wherein the collecting areaincludes collecting strips and the non-collecting area includesnon-collecting strips, the non-collecting strips having at least oneinsulating layer associated therewith, wherein the collecting strips arewider than the non-collecting strips.
 15. The radiation detectorassembly of claim 12, wherein the non-collecting area is larger than thecollecting area.
 16. The radiation detector assembly of claim 15,wherein the collecting area includes collecting strips and thenon-collecting area includes non-collecting strips, the non-collectingstrips having at least one insulating layer associated therewith,wherein the non-collecting strips are wider than the collecting strips.17. A method comprising: providing a semiconductor substrate having asurface; providing anode unit cells on the surface of the semiconductorsubstrate, each anode unit cell comprising anode portions, the anodeportions configured to receive electrical charge responsive toabsorption of a photon, the anode portions of each anode unit cellincluding at least one collecting portion and at least onenon-collecting portion; arranging the anode unit cells into pixelatedanodes, wherein the anode portions of each anode unit cell includecollecting portions and non-collecting portions, wherein the collectingportion of each anode unit cell includes a central collecting area,wherein at least one of the collecting portions and at least one of thenon-collecting portions of each anode unit cell form portions ofdifferent pixels; and disposing a collimator above the surface on whichthe anode portions are provided, wherein each pixel is defined by anopening of a collimator placed above the unit-cells.
 18. The method ofclaim 17, further comprising disposing a printed circuit board disposedopposite the surface of the semiconductor detector above which thecollimator is disposed, and electrically coupling the central collectingarea of each anode unit cell to the printed circuit board.
 19. Themethod of claim 18, further comprising providing an insulating layerinterposed between the non-collecting portion and the surface of thesemiconductor detector on which the anodes are disposed, but notproviding an insulating layer between the non-collecting portion and theprinted circuit board.
 20. The method of claim 17, wherein thecollecting portion defines a collecting area and the non-collectingportion defines a non-collecting area, and wherein the collecting areaand the non-collecting area have different sizes from each other.